Optical Radiation and Health Notes by KG Madam

7/31/2019 Optical Radiation and Health Notes by KG Madam

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JADAVPUR UNIVERSITY

M.E.( ILLUMINATION ) ,YEAR :2011 -12

BY KAMALIKA GHOSH

SUBJECT : OPTICAL RADIATION AND HEALTH

SYLLABUS

PART I

1. Optical

Radiation-UV

2. Visual -IR 3. IR- Source 4. UV- Source 5. Effect on

Micro -organization

6.GermicidalUV Radiation

7. Green House 8. GrowthRoom Photo

Period Lighting

9. MaximumLighting

10.MaximumLighting &

TerariumLighting

PART II

1.UV,IR-Effecton Human Eye

2.UV,IR-Effecton Human Skin

3.Vitamin D 4. CalciumMetabolism

5.BiologicalRhythm

6. Shift Work 7. Jetlag 8.InsectResponse

9.Decoy Lamp 10. Insect Trap

PART III

1. Light PhotoTherapy

2. Effect on eggproduction

3. Chicken Growth& Development

4. Effect onplant plant

response

5. Plant

Lighting

6. Green House

and growth roomphotoperiod

lighting

7.Maximum

Lighting andTerrarium Lighting


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LI GHT POLLUTI ON

New York City

Light Pollution ( also known as Photo Pollution , Luminous Pollution , etc .) is

excess or obtrusive light created by humans .Like other pollutions , it is a side

effect of careless industrial civilization .It comes from sources of poorly designedcrude lighting of offices , factories , street ,sporting venues , domestic ,etc.

Among other effects , it can obscure all but a few stars to city dwellers , render

astronomical observatoris , disrupt ecosystem etc.

Types o f l i gh t po l lu t ion

Light pollution is a broad term that refers to multiple problems, all of which are caused by inefficient,

unappealing, or (arguably) unnecessary use of artificial light. Specific categories of light pollutioninclude light trespass, over-illumination, glare, clutter, and sky glow. A single offending light source

often falls into more than one of these categories.

Light trespass occurs when unwanted light enters one's property, for instance, by shining over a

neighbour's fence. A common light trespass problem occurs when a strong light enters the window of

one's home from outside, causing problems such as

Light trespass

sleep deprivation or the blocking of an eveningview.
http://en.wikipedia.org/wiki/New_York_Cityhttp://en.wikipedia.org/wiki/New_York_Cityhttp://en.wikipedia.org/wiki/Light_pollution#Light_trespass#Light_trespasshttp://en.wikipedia.org/wiki/Light_pollution#Over-illumination#Over-illuminationhttp://en.wikipedia.org/wiki/Light_pollution#Glare#Glarehttp://en.wikipedia.org/wiki/Light_pollution#Clutter#Clutterhttp://en.wikipedia.org/wiki/Light_pollution#Sky_glow#Sky_glowhttp://en.wikipedia.org/wiki/Sleep_deprivationhttp://en.wikipedia.org/wiki/Sleep_deprivationhttp://en.wikipedia.org/wiki/Sleep_deprivationhttp://en.wikipedia.org/wiki/Light_pollution#Sky_glow#Sky_glowhttp://en.wikipedia.org/wiki/Light_pollution#Clutter#Clutterhttp://en.wikipedia.org/wiki/Light_pollution#Glare#Glarehttp://en.wikipedia.org/wiki/Light_pollution#Over-illumination#Over-illuminationhttp://en.wikipedia.org/wiki/Light_pollution#Light_trespass#Light_trespasshttp://en.wikipedia.org/wiki/New_York_City


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OVER-ILLUMINATION

Nijmegen, the Netherlands

Over-illumination is the excessive use of light.

Over-illumination stems from several factors:

Not using timers, occupancy sensors or other controls to extinguish lighting when not needed Improper design, especially ofworkplace spaces, by specifying higher levels of light thanneeded for a given task

Incorrect choice offixtures or light bulbs, which do not direct light into areas as needed Improper selection of hardware to utilize more energy than needed to accomplish the lighting

task

Incomplete training of building managers and occupants to use lighting systems efficiently Inadequate lighting maintenance resulting in increased stray light and energy costs

Most of these issues can be readily corrected with available, inexpensive technology; however, there isconsiderable inertia in the field of lighting design and with landlord/tenant practices that create

barriers to rapid correction of these matters. Most importantly public awareness would need toimprove for industrialized countries to realize the large payoff in reducing over-illumination.

Glare is often the result of excessive contrast between bright and dark areas in the field of view. For

example, glare can be associated with directly viewing the filament of an unshielded or badly shieldedlight. Light shining into the eyes of pedestrians and drivers can obscure

GLARE

night vision for up to an hour

after exposure. Caused by high contrast between light and dark areas, glare can also make it difficultfor the human eye to adjust to the differences in brightness. Glare is particularly an issue in road

safety, as bright and/or badly shielded lights around roads may partially blind drivers or pedestriansunexpectedly, and contribute to accidents.
http://en.wikipedia.org/wiki/Nijmegenhttp://en.wikipedia.org/wiki/Nijmegenhttp://en.wikipedia.org/wiki/Motion_detectionhttp://en.wikipedia.org/wiki/Lightinghttp://en.wikipedia.org/wiki/Officehttp://en.wikipedia.org/wiki/Light_fixturehttp://en.wikipedia.org/wiki/Lamp_%28electrical_component%29http://en.wikipedia.org/wiki/Night_visionhttp://en.wikipedia.org/wiki/Night_visionhttp://en.wikipedia.org/wiki/Human_eyehttp://en.wikipedia.org/wiki/Human_eyehttp://en.wikipedia.org/wiki/Night_visionhttp://en.wikipedia.org/wiki/Lamp_%28electrical_component%29http://en.wikipedia.org/wiki/Light_fixturehttp://en.wikipedia.org/wiki/Officehttp://en.wikipedia.org/wiki/Lightinghttp://en.wikipedia.org/wiki/Motion_detectionhttp://en.wikipedia.org/wiki/Nijmegen


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Glare can also result in reduced contrast, due to light scattering in the eye by excessive brightness, or

to reflection of light from dark areas in the field of vision, with luminance similar to the backgroundluminance.

The degree of Glare may be subdivided as follows :

(i) Blinding Glare describes effects such as that caused by staring into the Sun. It is completelyblinding and leaves temporary or permanent vision deficiencies.

(ii) Disability Glare describes effects such as being blinded by an oncoming cars lights, or lightscattering in fog or in the eye reduces contrast, as well as reflections from print and other dark areas

that render them bright, with significant reduction in sight capabilities.

(iii) Discomfort Glare does not typically cause a dangerous situation in itself, and is annoying and

irritating at best. It can potentially cause fatigue if experienced over extended periods.

CLUTTER

Clutter refers to excessive groupings of lights. Groupings of lights may generate confusion, distract

from obstacles (including those that they may be intended to illuminate), and potentially cause

accidents. Clutter is particularly noticeable on roads where the street lights are badly designed, or
http://en.wikipedia.org/wiki/Sunhttp://en.wikipedia.org/wiki/Clutterhttp://en.wikipedia.org/wiki/Accidentshttp://en.wikipedia.org/wiki/Roadhttp://en.wikipedia.org/wiki/Roadhttp://en.wikipedia.org/wiki/Accidentshttp://en.wikipedia.org/wiki/Clutterhttp://en.wikipedia.org/wiki/Sun


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Life exists with natural patterns of light and dark, so disruption of those patterns influences many

aspects of animal behavior. Light pollution can confuse animal navigation, alter competitiveinteractions, change predator-prey relations, and influence animal physiology.

Disruption of various ecosystems

Effect on astronomy

Due to sky glow Astronomers are unable to visualise star , planet etc . That is the reason

Reducing light pollution implies many things, such as reducing sky glow, reducing glare, reducing

light trespass, and reducing clutter. The method for best reducing light pollution, therefore, depends onexactly what the problem is in any given instance. Possible solutions include:

REDUCI NG LI GHT POLLUTI ON

Utilizing light sources of minimum intensity necessary to accomplish the light's purpose. Turning lights off using a timer or occupancy sensor or manually when not needed.

Improving lighting fixtures, so that they direct their light more accurately towards where it isneeded, and with less side effects.

Adjusting the type of lights used, so that the light waves emitted are those that are less likely tocause severe light pollution problems.

Evaluating existing lighting plans, and re-designing some or all of the plans depending onwhether existing light is actually needed.

OPTICAL RADIATIONS

Life has evolved under the influence of radiation from Sun . As a result Men , Animals , Plants havedeveloped a variety of complex physiological responses to Solar Radiations .

Light is an Electromagnetic Radiation .


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Optical Radiation divided into three parts :

OPTICAL RADIATION 100 nm 1mm

Ultra Violet (UV) Radiation

UV - CUV - B

UV - A

100 nm 380 nm

100 nm 280 nm280 nm 315 nm

315 nm 380 nm

Visible Radiation ( Light ) 380 nm 780 nm

Infra Red Radiation ( IR )

IR - A

IR - B

IR - C

780 nm 1mm

780 nm 1.4 mm

1.4mm 3.0 mm

3.0mm 1.0 mmn( nano) = 10 Exp(-)9 ;

m ( micro) = 10 Exp(-)6 ;

m( mili) = 10 Exp(-)3

Light by definition is visible radiation , hence it is incorrect ( but common ) to speak of "Ultra violetLight " or "Infra Red Light ". Ultra violet , Visible and Infra Red Radiation collectively known as

Optical radiation .The spectral region of wave lengths shorter than approximately 100 nm is termedionizing radiation , and wave lengths longer than 100nm are placed in the non-ionizing radiation

spectrum .These terms are useful for those who wish to distinguish between the Biological Effects ofdifferent types of radiation .


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From the whole optical waveband , the portion for which the atmosphere of the earth is transparent

,i.e., 0.29 - 1.4 mm (i.e., UV-B and IR - A ) plays the most important part .

The optical radiation is a prerequisite for life on the Earth .It meets the demand of energy for theorganic substances and is therefore the basis of our nutrition .

LAWS RELATED TO OPTICAL RADIATION

Actinic effects of optical radiations considering its absorption can be primarily classified as follows :

a) Active absorption : It effects a photochemical change within an essential part of the absorbingmedium , i.e., it acts actinically .

b) Passive absorption : It exists when the absorbing material acts only as a filter as a consequence

of which its temperature rises .Some laws , which optical radiation obeys are discussed below :

1) Law of Grotthus - Draper : This law states only such radiation can act photo chemically whenit is absorbed by the substance . This law sounds self evident but it is often disregarded when

effects of electromagnetic radiation are discussed . For instance radio waves or cosmic radiationare harmless for men or animals , because all organic tissue is penetrated without absorption .

2) Law of Van Kreveld : A second law which is valid for many photochemical andphotobiological processes is the law of Van Kreveld .The effects of single wavelength bands can

be added to an overall effect , as far as the single effects turn out to be independent from each other

.This means at the same time there should not exist conductive , i.e. catalytic or hindering(antagonistic ) effects .


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The Van Kreveld law is not more than a sum (additive ) law and as expressionfor the existence of an integral of the form :

S * s() d

Where Sis the relative spectral power distribution of the radiation ,

and s(

3) Law of Bunsen Roscoe :

)is the spectral power sensitivity of a photochemical , photobiological or a photo-voltaicreceiver for a certain effect.

As the law always refers to the same degree of a certain effect (e.g., to the same degree of erythema ofthe skin ) the characteristic of the sensitivity does not matter , i.e. it has not to be a linear function .

Photochemical and photobiological effect depend on the number of influencing photons on theirenergy on the degree of their absorption as well as on the sort of their relesed effect .

Therefore they depend on :the irradiance E,

the exposure time t

the spectral power distribution S and the spectral power sensitivity , s() (action spectrum) .As the exchange of reaction in the first sight depends on the number of influencing photons it does not

matter whether the same number of photons is absorbed within a shorter or within a longer time.Therefore in many actinic reactions the released effect is only dependent on the product of irradiance

E and the exposure time t, this means on the exposure H e or the dose . So for the present theBunsen Roscoe law is valid , which means that the actinic effect is the same , when the exposure

He is constant and if S4) Absorption ,Transmission , Depth of penetration and Spectral sensitivity (action spectrum):

does not vary with time .

As already discussed only absorbed radiation can become effective actinically .The depth of

penetration ,the degree of absorption or transmission of radiation may strongly depend on the wavelength .

Considering a cross section of the human skin with its various layers and depth of penetrationas a function of the wavelength ,one recognizes that UV C does not penetrate into the epidermis , it

is absorbed in the outer horny layer which consists of dead horny cells .UV B on the contrarypenetrates into the epidermis and UV A even into the underlying tissue .


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The spectral sensitivity or the action spectrum s(

ORGAN WHICH IS MOSTLY RESPONSIBLE FOR ACCEPTING LIGHT IS EYE .

) , as known for several photochemicaland photobiological effects is not but the reciprocal value of the exposure within a small wavelength

band to obtain a certain degree of a certain effect inmost cases normalised to the wavelength of

maximum sensitivity , max.

STRUCTURE OF HUMAN EYE

Fig . Cross Section ( Sagittal Section )

Eye ball is located at the orbital cavity of skull . More than 80% embedded within the skull about20% exposed outside .

Eye consists of two parts :

1) Light transmitting part / Dioptric System

2) Light receiving part Retina

The wall of Eye-ballconsists of three coats Sclera , Choroid and Retina from outside to inward .

Sclera :Thickness -1mm . It is a fibrous coat .Its anterior 1/6th portion called Cornea , is transparent

so that light can enter through it . Cornea is convex anteriorly and is devoid of blood vessels .Theposterior 5/6 th portion of Sclera is opaque .The part of Sclera exposed outside the orbit is covered by

a thin mucous membrane , called conjunctiva .


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Choroid : Thickness - 0.05mm .The middle coat of eyeball is choroid .It is highly vascular andpigmented .Due to presence of melanin pigments in the cells of the choroid it is dark in colour and

makes the interior of the eye ball a dark chamber .It has a rich supply of blood vessels and nourish theretina .

Iris : The anterior part of choroid lying behind the cornea is called iris which looks like a dark

coloured disc in frontal view .The diaphragm , governs the colour of eye, e.g., black . At the centre ofthe iris there is a small aperture called pupil , thorugh which light enters in side eye ball

Ciliary Muscle : It adjust the curvature of the lens ; increases the curvature of lens during close workand decrease when intense light fall on eye..

Retina : It is the innermost coat of eyeball made up of nervous tissues .It contains light sensitive layerNervous system containing photoreceptors Rod and Cone .

Both Rod ( 120 million ) and Cone ( 5 million ) contain visual pigments which arecapable of absorbing incident light and converting it into small electrical potentials.Light entering Rod

and Cone cell produces electric pulses through nerve systems , it goes to Cerebral cortex of the Brain .

Rod --- Rod cells are more Photo sensitive and spread through out the retina butpredominates at peripheral region of eye ball . Rods are sensitive to dim light

and hence responsible even for night vision .

Cone --- Cone cells are more colour sensitive and dominated at Fovea region .It is responsible for Day / bright light vision as they are excited by bright light

only but sensitive to colour .Cone Cells are of three types as follows :

Red corpuses -sensitive to light wave length 575 nm ,Green corpuses - sensitive to light wave length 540 nm ,

Blue corpuses - sensitive to light wave length 430 nm


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The part of retina at the posterior pole of eye ball is yellowish in colour is called yellow spot or

Macula Lutea .

At the centre of the Macula Lutea , there is a small depression called Fovea Centralis , which

contains cone cells only and no rod cell .It is very important considering its visual acuity ( oraccuracy of vision ) and colour vision .

A little medial to the fovea (15o) there is a small zone of retina called optic disc , through which

optic nerves pass out of the eye-ball , and blood vessels also passes in and out .


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The optic disc is totally devoid of photorecptors , so it is not capable of arousing any visualsensation called Blind Spot . Concentration of Rod and cone is zero here . It is 15 degree off from

central line .

Rod cell is usually predominated in the retina except at Yellow and Blind spot .

.The space between cornea and iris is called anterior chamber whereas that between iris and lens iscalled posterior chamber .These two chambers are interconnected through the pupil and they contain a

slight alkaline - watery fluid , called Aqueous humor .

Behind the lens there is a large cavity , the vitreous chamber which is filled with atransparent jelly like material called vitreous humor .

PROCESS OF VISUAL SENSATION

When the light reflected from an object falls on the eye , it passes through the refraction media of eyeball , namely ---cornea , aqueous humor , lens and vitreous humor and is finally focused on the retina

to form an image . The human eyes works as a Pin hole camera in which the pupil serves as a Pin hole.As the light falls on retina , the rods and cones becomes excited and generate nerve impulse that are

passes through the optic nerves to the brain .These impulses are finally transmitted to the visual centrein the occipital lobe of Cerebral Cortex and the visual sensation is arosed .

Although the image formation in the retina is inverted one , the brain learns to see it as noninverted .Rods and Cones contain photosensitive visual pigments called Rhodopsin and Iodopsin ,respectively.


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When light falls on the retinal receptors , the visual pigments are broken down into their components(Retinene and Opsin ) and thus bleached . This helps in generation of visual impulses in the receptors

and the optic nerve .In dark (i.e., when eyes are closed ) the pigments are resynthesized for being

reused .The breakdown and resynthesis of the visual pigments in light and dark is referred to as thephotochemical cycle of retina (or Photo Chemistry of Vision).

The concentration of Rod and Cone cells in Retina is not evenly distributed .Concentration ofCone cell is highest at the Fovea .Rod is almost zero there .Concentration of Rod cell is high at the

peripheral zone , ie closed to iris and concentration of cone cell is almost zero . Midway regionconsists of both rod and cone .


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When a person enters inside a dark room from a bright one initially he can not see at all , aftersometimes he can able to see because in bright room light falls in the fovea portion of retina and

person is capable of visualizing the object clearly as well as with its colour due to presence of conecell at fovea .

When he more to dark room initially inadequate light falls at fovea .But rod cell in the outerperiphery become active after a short a short white and person can visualize but due to absence ofcone cell (colour sensitive ) colour of the object can not be properly visualized .

STRUCTURE OF THE CORNEA

Although the cornea is clear and seems to lack substance, it is actually a highly organizedgroup of cells and protein. The cornea receives its nourishment from the tears and aqueoushumor that fills the chamber behind it. Unlike most tissues in the body, the cornea containsno blood vessels to nourish or protect it against infection. It must remain transparent torefract light properly, and the presence of even the tiniest capillaries would interfere with thisprocess.

HOW IMPORTANT IS THE CORNEA TO GOOD VISION ?

The cornea is essential to good vision. As the eye's outermost tissue, the cornea functionslike a window that controls the entry of light into the eye. For example, the cornea filters outsome of the most damaging ultraviolet (UV) wavelengths in sunlight. Without this protection,the crystalline lens and the retina would be highly susceptible to injury from UV radiation.

If this "window" is curved too much, as is the case in some nearsighted people, farawayobjects will appear blurry because distant light waves will refract imperfectly on the retina. If

this "window" has imperfections or irregularities, as is the case in people with an astigmatism,light will refract unequally, causing a slight distortion of the visual image. But, if this "window"is of normal shape and curvature, light will refract with exquisite precision to the crystallinelens.

LIGHT ADAPTATIONOur vision may be classified as Photopic , Scotopic and Mesopic , according to the process of

adaptation takes place .

Photopic vision :

This operating state of the visual system occurs at luminance higher than approximately3Cd / m

2at 555nm wavelength with Photo sensitivity of 100%

At these luminances , the retina response is dominated by the cone photo receptors .

The retina contains three different (LMS) type of cone each contains different combination of opsinand retinene .Each combination has a maximum absorption of light of different wave length .This

means colour is perceived and fine details can also be resolved in the fovea .


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Scotopic vision :

This operating state of visual system occurs at luminances less than 0.001 Cd / m2.For these luminances only the rod photoreceptors respond to stimulation , so that

Fovea of the retina is in operative . There is no perception of colour .

Mesopic vision : This operating state of the visual system is intermediate between the Photopic andScotopic visionary states . In mesopic state both cone and rod photoreceptor are active .As luminance

decline through the mesopic region , the fovea , which contains only cone photoreceptors , slowlydeclines in absolute sensitivity without significant change in spectral sensitivity , until vision fails

altogether , as the Scotopic vision is reached .In the periphery , the rod photoreceptors gradually cometo dominate the cone photoreceptors , resulting in gradual detoriation in color vision and resolution

and a shift in spectral sensitivity to shorter length .The change between sensitivities of the light adopted and dark adopted eyes is referred to as the

Purkinje Shift .

VISUAL THRESHOLDVisual Threshold is the minimum amount of light energy required to evoke the visual sensation .

In the dark adopted eye (Scotopic vision) the peak sensitivity occurs at wavelength of 505nm.Peak sensitivity of normal eye for light adopted ( Photopic vision ) of 555nm .

The level of visual threshold is influenced by :a) the wavelength of the light stimulusb) the state of adaptation of the eyec) that part of the retina which is stimulatedd) the size of the light stimulus , ande) the duration of the light stimulus


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SPECTRAL SENSITIVITY OF EYEThe eye contains rod and cone cells . Rod cells being used for low luminance , i.e., night time vision .

The relative sensitivity of Rods and Cones is given below :

Retina contains three different types of cells each containing a different combination of Opsin and

Retinene .Each of the combinations has a maximum absorption of light of a different wavelength.Detection of intermediate colors is achieved by utilizing a combination of the three types of cones .

For example :

Red + Green = Yellow1-1 Red + 1 Green = Orange

Spectral sensitivity of Rod Cell is about 10 times more than that of cone cell.

VISUAL DISCRIMINATIONS

The term given to the ability of the retina to distinguish between certain visual stimuli.Three types of visual discrimination a are under consideration :

1) Light discrimination2) Spatial discrimination

3) Temporal discrimination

1) Light discrimination :is the term given to the ability of the eye to detect a very weak / fible light source.

2) Spatial discrimination :

To recognize the space of an object , e.g., A

3) Temporal discrimination :Ability to detect sensation produced as a consequence of time varying stimuli ,e.g., The flickering of the picture on a television screen is so fast that the visual system detects

this as one continuous picture .


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ROLE IN MAKING THE EYES TO SEE THE TARGETEye movement can take several different forms , more important are :

1) Saccades : High velocity movements , usually generated to move the line of sight from onetarget to another .e.g., Black cat security guard

2) Pursuit : Smooth eye movements called pursuits and are used to follow a smoothly moving

target . For these movements , two eyes make equal movements in their angle ofconvergence .3) Vergence movement : Movement of the two eyes that keep the primary lines of sight

converged on a target or that may be used to switch fixation from a target at one distance toa new target at a different distance . Vergence movements play a major role in making the

eyes to see the target .

PERSISTANCE OF VISIONTemporal summation of eye is 1/10 second . If flicking is below that man can not distinguish.

Flicker :If the retina is stimulated by flushes of intermitted light a particular rate of stimulation , a sensation of

flicker will be arosed .(For single brief flashes of light less than 100ms ) any combination ofLuminance (L) and flush duration (t) with the same .

Light object produces the same perception .This characteristic is known as Blocks Law :

L * t = ConstantThe value of frequency at which the flicker becomes an apparently continuous. Signal is referred to

as the CFF Critical Fusion Frequency

CEF varies with :1) Light Intensity2) Size of stimulus , and3) Wave length

The approximate range of CFF values is between :

15 Flushes / Second , for low intensity simulation , at periphery of eyeto 60 Flushes / Second , for high intensity simulation , at fovea

This is the reason Florescent lamp with Electronic Ballast is preferred .

STROBOSCOPIC EFFECT

If the rate of flicker reaches a value which coincides with the angular velocity of rotating machinery ,

the stroboscopic effect is likely to be produced and the shaft of the rotating machinery will appear tobe stationary when it is actually moving . This can have disastrous consequences .

Disc rotating at a speed which coincides with pulse rate output of light from stroboscopic source and

therefore cross appears to be stationary .

Fortunately there are some simple methods of preventing the stroboscopic effect from occurring ,including:


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1) Connecting adjacent single lamp luminairs to different phases of the electrical supply .2) Using Lead lag circuitry in the control gear of the luminaire which Phase shifts the

electrical supply between adjacent lamps in the same luminaire.

3) Introducing a non pulsating light source in the vicinity of the rotating equipment .

Typically this is achieved with a Tungsten filament lamp which is unlikely to give rise toflicker in the lamp output since the filament has considerable thermal inertia , which leads to good

stability in the luminous output .

Daylight is also a nonpulsating light source and the stroboscopic effect is much less problematic inworkshops which have windows admitting natural light to the interior .

Uses :

1. Adjusting and setting of the tunning of the engine of a motor vehicle.2. Remote measurement of the speed of a rotating shaft .

OPTICAL PERFORMANCE OF EYES

When the lens system is normal the eye should recognize detail of angular size 0.5 minute of arc orless. Angular size is the size as seen and is a function of both size and viewing distance .The above

figure illustrates using a standard test symbol called a Landolt Broken Circle . An optician will testa persons sight by his ability to recognize letters on a standard test chart .

A person who has vision 6:6 can recognize an 8.75mm letter at a distance of 6m and 6:12 meanshe can only read at 6m what a 6:6 person can read at 12m ,i.e., the eye sight is substandard .


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In experiments on vision and visual performance the process of recognition is normally describedin terms of visual acuity , where ,

1Visual Acuity = ---------------------------------------

Angular size (in minutes)

Therefore the starting point in understanding lighting is to appreciate that the eye must be functioningproperly.

DEFECTS AND ANOMALIES OF VISIONS

Glare :is a development of contrast . Normally the eye adapts to whatever it is viewing , but if the taskor background are too bright or the contrast is too great , vision suffers either by the situation

becoming visually uncomfortable or by the task becoming different to see or both . Thus Glare occursdue to excessive high luminance contract . It can be classified as :

a) Disability Glare & (b) Discomfort Glare

a) Disability Glare or Induction

If a high luminance source is suddenly introduced into the field of view , the adaptationlevel of the eye will tend to raise , more so in the retina area of the image of the source (of glare ) and

as a consequence the smallest detectable difference in luminance will be higher than that appliedbefore the introduction of the glare source .It will be evident that much of the field of view which

could previously be seen clearly will now become invisible .Disability Glare can come directly from a light source , or window , or by reflection off a

glossy surface (veiling reflection ).The modern office with its array of visual display units (VDU) isa common situation where this problem must be considered .

Contrast Sensitivity Function (CSF) is one aspect of design where veiling glare is recognizedand accounted for in the design process .

VARIOUS REFLECTIVE ERRORS

a) MYOPIA (Near sighted ness)Myopia , nearsightedness is a vision problem experienced by upto about 1/3 rd of the population.Myopic people suffers from long distance visionary problem but no complain for close work .


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Cause : Myopia Occurs either when the refractive index of lens is higher compared to normal orthe eyeball is slightly longer than usual from front to back . This causes light rays to focus at a


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point before the retina , rather than directly on its surface. Good students suffer from myopia dueto stress on the eyes for excessive reading .

Both genetic and environmental factors play a role in the presence and progression ofmyopia .

Treatment : Myopia can be corrected with concave ( Minus power )glasses , contact lenses or

refractive surgery , LASIK- Laser Assisted in Situ Keratomileusis . MyopiaAffects between 10 40 yrs. And after 45 yrs. It tends to decrease .

B) HYPERMETROPIA : If the eye ball is smaller or refractive index is poor the image isfocused behind the eyeball making blurred image on the retina . In this case near vision is more

affected than the distance vision and so these people are known as farsighted . These patients needconvex (plus ) lenses in front of eye to make a clear image .

C) PRESBYOPIA : The eye deteriorates with age .Any one born with normal eyesight can expect to

be wearing glasses by the time they reaches at the age of 40 years . This is mainly due to weakening ofthe ciliary muscles and quality of lens a difficulty is being able to focus at short distances .

Causes : Hardening of the crystalline lens as well as weakening of the ciliary muscles due to agingcauses difficult for ciliary muscles to alter the focus of the lens properly.

Presbyopia occurs in addition to any existing vision defect and the usual symptoms associatedwith Presbyopia include :

1.Blurred vision at the usual reading distance .2. A necessity to hold reading material progressively further away .

3. Headaches4. Visual fatigue when performing closure task.

Ready : Use of Convex Lens .Most of theses refractive errors can be corrected by the use of spectacles or contact lens .


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D )ASTIGMATISM :

Definition : Astigmatism usually occurs when the front surface of the eyes , the cornea , has anirregular curvature . Astigmatism is one of a group of eye condition known as refractive errors .

Refractive errors cause a disturbance in the way that light rays are focused within the eye .

Astigmatism often occurs with nearsightedness and farsightedness , conditions also resulting fromrefractive errors . Astigmatism is not a disease .It simply means that you have a variation ordisturbance in the shape of cornea .


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Causes : Astigmatism occurs when the front surface of the eye , the cornea , has an irregularcurvature . Normally the cornea is smooth and equally curved in all directions and light entering

the cornea is focused equally on all planes , or in all directions .In

Astigmatism the front surface of the cornea is curved more in one direction than in the other .Thisabnormality may result in vision that is much like looking into a distorted , wavy mirror .Thedistortion results because of an inability of the eye to focus light rays to a point .

If the corneal surface has a high degree of variation in its curvature , light refractionmay be impaired to the degree that corrective lenses are needed to help focus light rays better .At any

time , only a small proportion of the rays are focused and the remainder are not , so that the imageformed is always blurred .Usually Astigmatism causes blurred vision at all distance .

Astigmatism is very common .Some experts believe that almost every one has a degree ofAstigmatism, often from birth , which may remain as it is throughout life .The exact reason for

differences in corneal shape remains unknown but the tendency to develop Astigmatism is inherited .Treatment : The corrective lenses needed when Astigmatism is present are called Toric lens

And have an additional power element called a cylinder .They have greater light bending power in oneaxis than in others . Refractive surgery may be able to correct some forms of Astigmatism .

Fan Line Test for Astigmatism : An individual with Astigmatism will see some lines of the fans asdistinctly black and other lines as grey .In this condition individual will also simultaneously interpret

equal length radial lines as having different lengths .This information will allow an optometrist to orient a cylindrical lens in order to correct the fault

.NOTE : Although when the eye is perfectly corrected for refractive errors , a residual blur can remain

due to Spherical and Chromatic Aberration .

LASIK - LASER ASSISTED IN SITU KERATOMILEUSISPhotorefractive Keratectomy (PPK)-a surgical technique using lasers to sculpt the cornea of the eye

and thus altering its refractive power , has been developed to correct refractive errors , .e.g .Myopiaand Astigmatism.

ABERRATIONS

1. CHROMATIC ABERRATION: Shorter wave length are refracted more than longer wavelengths.The result of different foci cause blur.


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NOTE : The above two aberrations are mainly of theoretical interest . They are partiallycompensated by the image processing of the visual system and usually can be neglected in practical

lighting design . These are important in certain specialized application , e.g. work under reducedilluminance when pupil is enlarged .

2. SPHERICAL ABERRATION : The rays that enter through the periphery of the cornea are

refracted more than those that enter through the central zones. Thus light in the retinal image ispartially redistributed over a large retinal area than would be the cause in an aberration free system

.The amount and type of Spherical Aberration varies with the state of accommodation .

DIPLOPIA :Good vision necessarily required the ability of both eyes to aim at the same targetsimultaneously .Essentially both eyes work as a team , and if this is not achieved , double vision (

diplopia) will exist or the brain will attempt to block out the image of one eye ( suppression ).In manyof the cases of double vision , the cause is an a consequence of some malfunction in the muscle or its

nervous control .Each of the two eyes has six extraocular muscles , and if they are not all functioningcorrectly , improper alignment will occur .

Double vision is a consequence of faulty alignment , is often very uncomfortable and the brain

will attempt to block off one image of the two present , in order to restore some degree of visualcomfort .In some cases extra muscular effort will be required in order to maintain correct alignment

which can lead to headaches and general visual discomfort.

COLOUR DISCOMFORT

1. Monochromats exhibits a total absence of colour appreciation and so the individual istotally colour blind .

2. Dichromats shows an absence , but not an abnormality of one factor in the cones , three(3)forms:

a) Protanope Red factor is absence

b) Deuteranope Green factor is absence


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c) Tritonope Blue factor is absence

3. Trichromats One factor has abnormality but not absence .Three(3) forms:a) Protanomalous Red factor is weak

b) Deuteranomalous Green factor is weak

c) Tritono malous Blue factor is absence

Anomalous trichromats exhibits a colour difference rather than a colour blindness .

There are various methods to test colour blindness , among them ISHIHARA Test is themost popular .

PARTIAL SIGHTEDNESS

1. CATARACT : The most common type of disorder occurs due to age when people reaches about

65 years.The lens is made mostly of water and protein . The protein is arranged to

allowe to allow light to allow light pass through and focus on the retina . Sometimes some of theprotein clu the protein clumps together and starts to develop Cloud (opacity develops) in a

small area of the lens . It may be that the protein in the Lens just changes as it ages .It is also related tovitamins and minerals .

Effect : It absorbs and scatters more light passing through the lens . It reduces

contrast sensitivity over the entire visual field because the scattered light degrades the contrast of theretina image causing disability glare .

Causes : 1) Age related2) Over exposure to IR radiation

3) Congenital cataract Some babies are born with cataractsor develop in childhood , often in both eyes .

4) Secondary Cataract - Cataracts are more likely to develop in people who havesome health problems , e.g., Diabetes , hypocalcemia , use of steroid , etc.

5) Traumatic cataract : Cataracts can develop soon after an eye injury , or years

later .


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TREATMENTS : Cloudy lens are removed by surgery and substitute artificial lens to implant in thefollowing methods .

Extra capsular Surgery ( PHACO) :

Doctors opens the front of the capsule and remove the lens , leaving the backof the capsule in place .Sound waves (Ultra sound ) may be used to soften andbreak up the cloudy lens so that it can be removed through a narrow hollow

tube . This is called phaco emulsification or Phaco.

Intra Capsular Surgery :

The entire lens is removed including the capsule . Although extracapsularsurgery has largely replaced this technique in the USA.It is safe and effective

and may be used in some cases , e.g., if the lens is too hard for Phaco surgery.

Currently , LASERs are still unable to remove a cataract . Although scientists are working on ways touse LASERs in cataract surgery .

2. MACULAR DEGENERATION :

This occurs when the macular photo receptor (s) and neurons become inoperative due to bleeding or

Altrophy .The fovea is at the centre of the macula lutea and any less of vision implies a serious reductionin visual acuity , colour vision and contrast sensitivity at high spatial frequencies . Typically these

changes make reading difficult , if not impossible . However peripheral vision is largely unaffected soway finding remain unchanged .

Providing more light , usually by way of task light , will help people in the early stage ofmacular degeneration to read , although as the deterioration progresses , additional light is less

effective . Increasing the visual size of the retinal image by magnification or by closure is helpful at


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all stages , because this can increase he size of the retinal image sufficiently to reach parts of the retinabeyond the macular .

Treatment : LASER ( YAG - Yttrium Aluminium Garnet ) at wave length of 537.5 nm can be usedas a Photo Dynamic Therapy to block further degeneration but can not revive the lost part .

Fluorescein angiography, or fluorescent angiography, is a technique for examining the circulation

of the retina using the dye tracing method. It involves injection of sodium fluorescein into the systemic

circulation, and then an angiogram is obtained by photographing the fluorescence emitted afterillumination of the retina with blue light at a wavelength of 490 nanometers. The fluorescein dye also

reappears 12-24 hours in the patient urine, causing a yellow-green appearance.

Fluorescein angiography is one of several health care applications of this dye, all of which have a riskof severe adverse effects. See fluorescein safety in health care applications.

3. GLAUCOMA :

The normal field of vision for eye is as follows :
http://en.wikipedia.org/wiki/Fluoresceinhttp://en.wikipedia.org/wiki/Angiographyhttp://en.wikipedia.org/wiki/Angiographyhttp://en.wikipedia.org/wiki/Retinahttp://en.wikipedia.org/wiki/Dye_tracinghttp://en.wikipedia.org/wiki/Fluoresceinhttp://en.wikipedia.org/wiki/Angiogramhttp://en.wikipedia.org/wiki/Fluorescencehttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Nanometerhttp://en.wikipedia.org/wiki/Health_carehttp://en.wikipedia.org/wiki/Adverse_effecthttp://en.wikipedia.org/wiki/Fluorescein#Safetyhttp://en.wikipedia.org/wiki/Fluorescein#Safetyhttp://en.wikipedia.org/wiki/Adverse_effecthttp://en.wikipedia.org/wiki/Health_carehttp://en.wikipedia.org/wiki/Nanometerhttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Fluorescencehttp://en.wikipedia.org/wiki/Angiogramhttp://en.wikipedia.org/wiki/Fluoresceinhttp://en.wikipedia.org/wiki/Dye_tracinghttp://en.wikipedia.org/wiki/Retinahttp://en.wikipedia.org/wiki/Angiographyhttp://en.wikipedia.org/wiki/Fluorescein


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In many people, increased pressure inside the eye causes glaucoma. In the front of the eye is a spacecalled the anterior chamber. A clear fluid flows continuously in and out of this space and nourishesnearby tissues .

The fluid leaves the anterior chamber at the angle where the cornea and iris meet. When the fluidreaches the angle, it flows through a spongy meshwork, like a drain, and leaves the eye.

Open-angle glaucoma gets its name because the angle that allows fluid to drain out of the anteriorchamber is open. However, for unknown reasons, the fluid passes too slowly through the meshworkdrain. As the fluid builds up, the pressure inside the eye rises. Unless the pressure at the front of the eyeis controlled, it can damage the optic nerve and cause vision loss.

Due to an increase in intraocular pressure retina starts to damage .1) It reduces field of vision .2) Poor night vision3) Sensitive to glare

VISUAL COMFORT

In order to ensure visual comfort it is necessary to ensure that the lighting allows a good level ofvisual performance and does not cause distraction .

This can be done by following ways :

1) Identify the visual tasks to be performed and then determine the characteristics of lightingneeded to allow a high level of visual performance of the task .

2) Eliminate flicker by using high frequency control gear for discharge lamp .3) Reduce disability / discomfort glare by proper lighting design.4) Reduce density and extent of shadows.

Use extended / wide light source Use more numbers of low wattage lamps.

5) Reduce veiling reflections by reducing the secular reflectance of the surface being viewedor by changing the geometry between the viewer , the surface being viewed or by increasing

the amount of inter - reflected light in the space.6) If the reflections are occurring on a self luminous surface such as VDT Screen

Use dark letters on a bright background . This will reduce the impact of any veilingreflections seen on the screen .


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GUIDE LINES FOR ACCEPTABLE LIGHTINGThere have be been a number of studies that have examined the acceptability of the specified

aspects of lighting , usually in a specified context . This section considers what is knownabout the preference for three lighting variables , all of which are under the control of the

lighting design .

1) Illuminance : The Acceptability of different illuminances in offices and other workingareas has been examined and tried to determine the effect of illuminance on the observerpreference .

2) Spatial Distribution :

Spatial distribution of illuminance across the working area is also important . In general themore uniform the light distribution in the visual field and the larger the area of the visual

field it covers , the better one sees the visual task table , no shadow.


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3) Colour of Illumination :The colour of illumination can be described by two independent properties :

The colour of illumination can be described by two independent properties :

a) Chromaticity / Correlated Colour Temperature i.e., Colour appearance of lightsource Warm for lowCCT Value , Cool for High CCT Value .

b)Colour Rendering Index : It refers to the ability of a light source with its particular

CCT to render the colours of objects the same as reference light source of the sameCCT .

Experiments showed that lamps with high CCT values at low illuminances will make a

space appear cold and dim .

Conversely low CCT lamp with high luminance will make the space appearartificial and over colourful.

OPTICAL RADIATION AND HAZARDS ON EYES

There are basically four separate type of hazards to the eye that must be considered for each opticalsource :

1. Ultra - violet radiation hazards to the cornea and lens (at 200 400 nm ) .2. Thermal retinal injury hazard (at 400 1400 nm ) .3. Blue light photo chemical retinal hazard (principally at 400 550 nm ) .4. Near infrared hazards to the cornea and lens (at 700 3000 nm ) .

EFFECT OF UV - RADIATION ON EYES

a) PHOTO CONJUNCTIVITIES - Normally the human skin is protected by the upper layer , i.e.the horny layer (stratum corneum), this is not the eye bulb and the eye lid and the eye bulb itself is

not protected .Too strong UV radiation on the conjunctiva leads to the so called conjunctivitis , apainful inflammation of the conjunctiva , whose pair effects are described as sand in the eyes .

It is to be felt only after 5 10 hours after radiation, so that sleeping, reading and seeing arestrongly impeded (hampered) . The inflammation ceases according to its severe ness within a time

of half a day to several days.

b) PHOTOKERATITIS - Photokeratitis is an inflammation of the transparent cornea on the frontside of the eye bulb caused by UV radiation .The maximum of the relative effectiveness of the

photokeratitis lies at 270 nm and the threshold exposure at this wavelength amounts to about 50 J /m

2

.

c) LENTICULAR EFFECTS - Lenticular effects of UV radiation have been recently undergoingextensive investigation .The lens undergoes a number of changes with aging, including a yellowishcolouration, an increasing proportion of insoluble proteins, sclerosis

With loss of accommodation, and cataract ,etc.


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Some investigators are coming to believe that all wave length below 400 nm should be executedusing sunglass etc.

d) RETINAL EFFECTS Retinal effect of UV radiation areproblematical,

depending on whether enough photons reach the retina to produce an

observable effect. Under normal circumstances, the ocular media (Cornea,aqueous lens and vitreous) protect the retina from ultra violet exposure. In thenear ultraviolet (320-400 nm) the lens effectively shields the retina.

EFFECT OF IR - RADIATION ON THE EYES

The Ocular media absorb an increasing amount of the radiant energy incident upon the cornea for

increasing wave lengths in the near infrared (IR-A).

Wavelengths greater than 1400nm (i.e., IR B & C ) do not found involve the retina , but canproduce effects on the eye-lids to cornea / aqueous humour and lens causing lenticular damage

.Beyond 1900nm ( IR-B) the cornea is considered to be the sole absorber causing infrared cataract.Infra red cataract has been reported in the literature for a long time , but there is little or no recent

quantative data to substantiate the clinical observation .The general consequence is that long term exposure to infra red radiation produces an elevated

temperature in the lens which , over a period of years leads to denaturation (change in normalbehaviour ) of the lens proteins with consequent opacification . Some authorities believe that infrared

radiation is absorbed by pigmented iris and convert to heat which is conducted to the lens rather thanby direct absorption of radiation by the lens .

Infrared cataract is reported to occur among glass blowers , steel puddlers and others whoundergo long term occupational exposure to infra red radiation . It can be avoided by using the

proper IR protection filters .

EFFECT OF OPTICAL RADIATION ON SKIN

SKIN ANATOMYSkin is an ever changing organ that contains many specialized cells and structures . The skin functions

as a protective barrier that interfaces with a sometimes hostile environment .It is also involved inmaintaining the proper temperature for the body to function well .It gathers sensasonary information

from environment and plays as active role in the immune system protecting us from diseases .Skin hasthree (3) layers :

- Epidermis

- Dermis- Subcutaneous Tissue


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Epidermis is the outer layer of skin .The thickness of the epidermis varies in different types of skin. It is the thinnest on the eyelid at 0.05 mm and thickest on the palms and soles at 1.5 mm .Epidermis

contains 5 layers .

Epidermis composed of three ( 3 ) types of specialized cells .

- Melanocyte produces pigment ( melanin )- Langerthans cell is the frontline defense of the immune system in the skin

- Merkel cell - function is not clearly known.

Dermis varies in thickness depending on the location of skin . It is 0.3 mmon eyelid and 3.0 mm at the back .

Dermis composed of three ( 3 ) types of tissues .

- Collagen- Elastic Tissue &- Reticular Tissue

The dermis contains many specialized cells and structures. The hair follicles are situated here

muscle that attaches to each follicle .Sebaceous (oil) glands , and apocrine (scent) glands are a follicle . This layer also certain

eccrine (sweat) glands , Nerves transmit sensations of pain , itch , touch , pressure etc.

Subcutaneous Tissue thesubcutaneous Tissue is a layer of fat and connective tissue that houseslarger blood vessels . This layer is important in the regulation of temperature of the skin itself and the

body .


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EFFECT OF SUN ON THE SKIN

Sunlight has a profound effect on the skin .UV radiation exposure on skin has two advantages

- production of vitamin D- induction of protective pigmentation

Sunlight causes premature skin cancer , and a host of skin changes . Exposure to UV A & B

causes 90 % of the symptoms of premature skin aging .

UV C radiation is almost completely absorbed by the ozone layer and does notaffect the skin . But UV C itself has some carcinogenic effect .

UV B affects the outer layer of the skin and is the primary agent responsible for

skin damage.

UV A provides major contribution to skin damage deeper into the skin andwork with more intensity.

Both UV A & B radiation can cause skin damage including wrinkles , lowered immunity age skin

disorders and cancer .However we still do not fully understand the process .

Some of the mechanisms for UV skin damage are collagen breakdown , formation of free radicals

, DNA repair and inhibiting the immune system .


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Collagen BreakdownIn the dermis, UV radiation causes collagen to break down at a higher rate than with just chronologic

aging. Sunlight damages collagen fibers and causes the accumulation of abnormal elastin. When thissun-induced elastin accumulates, enzymes called metalloproteinases are produced in large quantities.

Normally, metalloproteinases remodel sun-injured skin by manufacturing and reforming collagen.

However, this process does not always work well and some of the metalloproteinases actually breakdown collagen. This results in the formation of disorganized collagen fibers known as solar scars.When the skin repeats this imperfect rebuilding process over and over wrinkles develop.

Free RadicalsUV radiation is one of the major creators of free radicals. Free radicals are unstable oxygen molecules

that have only one electron instead of two. Because electrons are found in pairs, the molecule mustscavenge other molecules for another electron. When the second molecule looses its electron to the

first molecule, it must then find another electron repeating the process. This process can damage cellfunction and alter genetic material. Free radical damage causes wrinkles by activating the

metalloproteinases that break down collagen. They cause cancer by changing the genetic material,RNA and DNA, of the cell.

DNA RepairUV radiation can affect enzymes that help repair damaged DNA. Studies are being conducted looking

into the role a specific enzyme called T4 endonuclease 5 (T4N5) has in repairing DNA.
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Immune System EffectsThe body has a defense system to attack developing cancer cells. These immune system factors

include white blood cells called T- lymphocytes and specialized skin cells in the dermis calledLangerhans cells. When the skin is exposed to sunlight, certain chemicals are released that suppress

these immune factors.

Cell DeathThe last line of defense of the immune system is a process called apoptosis. Apoptosis is a process ofcell-suicide that kills severely damaged cells so they cannot become cancerous. This cell-suicide is

seen when you peel after a sunburn. There are certain factors, including UV exposure, that prevent thiscell death allowing cells to continue to divide and possibly become cancerous.

Skin colour is genetically determined result of a number of factors , the primary factor is melanin

.Melanin protects against UV damage by reducing transmission through absorption and scattering .Its quality , granule size and distribution all affect skin colour .

EFFECTS ON INFRA - RED RADIATIONSpecial photochemical effects in the skin and the subcutaneous tissue by IR radiation can not be

provoked because of relatively low energy of the IR quantas . Most of the effects are the heating ofthe skin and the tissue by the absorbed radiation .

When the human body is irradiated by IR Radiation the natural temperature fall from the innerto the outer parts of the body is inverted .As a consequence the mechanism regulating the body

temperature begin to work , leading to a rush of blood in the outer blood vessels which is to be seen asheat erythema .

By IR radiation of the skin blood circulation , respiration , functions of stomach and intestines ,kidneys , muscles and nerves can be influenced . These effects can not only be explained purely

physically but also by irritations of the nerve ends in the skin thus influencing inner organs via a

reflectory system .
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SOME EXAMPLES OF OPTICAL RADIATION EXPOSURE

Sources Principal wave- Potential Potentially exposed

length bands effects populations

of concern

-----------------------------------------------------------------------

sunlight ultraviolet (UV), skin cancer; outdoor workers

visible cataract; (e.g., farmers,near-infrared sunburn; construction

accelerated workers); sun-

skin aging; bathers; general

solar retinitis population

-----------------------------------------------------------------------

arc lamps UV, visible, photokeratitis; printing plant

(Xe, Xe-Hg, near-infrared erythema; camera operators;

Hg) skin cancer; optical laboratory

retinal injury workers;

entertainers

-----------------------------------------------------------------------

germicidal actinic, far UV erythema; hospital workers;

(low-pressure photokeratitis; workers in sterile

Hg) skin cancer laboratories

medium- UV-A and blue retinal injury street lamp

pressure light replacement

Hg-HID lamps personnel; gymnasium

(broken actinic UVA photokeratitis; users; general

envelope) erythema population

-----------------------------------------------------------------------

carbon arcs UV, blue light photokeratitis; certain laboratory

erythema workers; search ight

operators

-----------------------------------------------------------------------

metal halide near UV, visible cataract; printing plant

UV-A lamps photosensitive maintenance workers;

skin reactions; integrated circuitretinal injury manufacturing

workers

-----------------------------------------------------------------------

sunlamps ultraviolet, photokeratitis; suntan-parlour

blue light erythema, customers; home

users

accelerated

skin aging;

skin cancer

-----------------------------------------------------------------------

welding arcs ultraviolet photokeratitis; welders' helpers;

and blue light erythema; welders

UV cataract;

retinal injury

-----------------------------------------------------------------------

industrial infrared radiant heat steel mill workers;

infrared stress; foundry workers;

sources infrared workers using

cataract infrared drying

equipment


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BIOLOGICAL RHYTHMS

Cyclic changes in biological parameters e.g.,(i) Day-Night Cycle(ii) Lunar Cycle

(iii) Seasonal CycleHave been observed across species throughout the plant and animal kingdoms known as BiologicalRhythms .

Biological Rhythms manifest themselves at both thea) macroscopic ( multi cellular)b) microscopic (unicellular or subcellular levels )

Each rhythm has a characteristic Amplitude or magnitude of periodic change and a CharacteristicPeriod or frequency of oscillation .

The timing of all Biological Rhythms involves the coordination , or entrainment of external time factor( called exogenous Zeitgebers )

internal peacemaker (endogenous)External causes are due to geographical effect as states earlier .Each natural cycle causes the synchronization of a particular rhythm called a

Circa-rhythms.

a) Circadian Rhythm ---Day-night effect manifested in(i) Plant - open / closing ; rising / lowering of leaves(ii) Animals --- Sleep / wake cycle is affected by light


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b) Circannual rhythms (Seasonal ) flowering , seed germination , breeding of certain animals .

Disruption of circadian rhythms not only affects sleep patterns but also has been found toprecipitate mania in people with Bipolar disorder (Manic depressive illness). Other types of

illnesses also are affected by circadian rhythms , e.g. Heart attacks occurs more frequently in the

morning while Asthma attacks occurs more often at night .There are other effects discussed in details afterwards .Although Biological clocks have been the focus of intensive research over the past four decades ,

only recently have the tools needed to examine the molecular basis of circadian rhythms becomeavailable . Early studies pointed to an area of the brain , the hypothalamus as the location of the

circadian pacemaker in mammals . More recent findings show proteins called Cytochromes ,located through out the body are also involved in detecting changes in light and setting the bodys

clock .Recent research has shown that some of our Ganglion Cells may be performing as a third type

of Photoreceptor called Intrinsically Photosensitive Retinal Ganglion Cells ( ipRGC) .Thesesparsely situated cells are most sensitive to Blue Light . They seem to exist principally to help us to

differentiate between day and night (thus modulating Sleep / Wake cycles) . The ipRGC hasbeen shown to independently control dilation and contraction of our pupils with a peak response at

480nm Blue light.

FEW DISORDERS DUE TO BIOLOGICAL RHYTHM

SAD Seasonal Affective DisorderWith the fall of winter people affected with malady experience , Melatonin secretion (sort of

hormone from Pineal Gland to be discussed later .)1) A certain decrease in their physical energy and stamina .2) Experience emotional depression , feeling of hopelessness and despair3) Increase sleepiness and need of sleep4) Increased appetite (particularly sweet / carbohydrates )

The SAD can be treated by light therapy . Earlier SAD can be treated with light located at a specificdistance with 2500 Lux 10,000 Lux on face .Exposure duration varies from 30 minute to 6 hour in

single or split sessions .2500 Lux with 2 4 hour

Or , 10,500 Lux with 30 minuteHowever it is still unknown which photo pigment / photo receptors mediate the antidepressant

effects of light .Earlier studies on SAD therapy used fluorescent lamps that emitted white light containing a small

portion of UV A energy. Those early findings erroneously led to the suggestion that UV-A isnecessary for successful therapy.


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The current literature however , clearly shows that SAD symptoms can be reduced by lamps thatemit little or no UV . Hence UV radiation does not appear to be necessarily for positive therapeutic

results.Most of the clinical trials treating winter depression have employed while light emitted by

commercially available lamps . The while light used for treating SAD can be provided by a range of

lamp including incandescent and cool white fluorescent .

There is an assortment of light devices specifically designed for the treatment of SAD . Light

therapy instruments come in a variety of shapes and configurations , including workstations , headmounted light visors and automatic dawn simulators . These devices are configured to shorten

therapeutic time , increase patient mobility or permit therapy during the sleep period .Light visors appear to therapeutically benefit SAD patients with substantially lower energy

requirements than those emitted by light boxes (2500 10,000 Lux ) and workstations.Since dose response comparisons have not been performed among different lamp types and light

devices , it is not yet decided which types of light superior for treating depression .There are numerous clinics in North America who offers light therapy from SAD .

SAD is prevalent when Vitamin D storage are typically low . Broad Spectrum light therapyincludes wave lengths between 280 320 nm which allows the skin to produce

Vitamin D .

LIGHT THERAPY FOR JET LAG , SHIFT WORK

AND SUSTAINED PERFORMANCES

Jetlag :is the condition that results from rapidly moving across time zones .Travelling across time

zones can interface with social and business schedules , disrupt circadian rhythms and consequentlyimpire both physical and psychological health . While the body readjusts its biological clock to a new

time zone , many people experience symptoms such as daylight sleepiness , night-time insomnia ,gastrointestinal distress , irritability , mild depression and confusion .


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Shift Work : similar to intercontinental travelers , shift workers are also forced to make changes to

their usual sleep and wake time .However , circadian disruption in shift workers is generally longerlasting and therefore , the body also requires a long period of time to readjust .

Problems of decreased productivity , increased accidents and serious healthconsequences . It has been observed that they suffers from higher incidence of :

- Cardiovascular Disease ,- Gastrointestial Disease ,

- Psychological Problems , Cancer etc.

Bright light exposure appears to have an acute stimulating alerting effect on healthy humans .

An early study showed that subjects working a continuous 30 Hour shift demonstrated behavioraland cognitive performance (reaction time , mathematical skills and complex problem solving ).

When working under 3000 Lux of white light as compared to a dimmer light exposure of

100 Lux .Similar problem occurs with Astronauts during long duration space flight .Emphasis hasbeen given on illumination of general living quarters as well as design of space vehicle windows ,

improve and space suit with visors for manned missions .Results from such studies also may berelevant to general Architectural lighting design on earth for civilian design on earth for civilian

problems of Shift work and Jet lag .

Night worker discharges better performance when exposed to 1000 to 12000 Lux than under dim lightof 100 150 Lux, specially at the brightness of 3000 5000 Lux level .However it is under research

how to best use light for both short term and long term work application .


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HORMONES

With the evolution of Multicellar higher organisms it has become necessary for them to have

mechanisms for maintenance of functional coordinatation between different cells , tissues and organs.For this higher animals are provided with two types of regulatory mechanisms through which

information are conveyed from one organ to another.The first one is the neutral mechanism which carries the information originating from one part

of the body to the other part very quickly in the form of nerve impulses ( like electric current ) for arapid regulation of various organs .

The second one is the blood-borne chemical (hormonal) mechanism in which chemicalsubstances secreted from certain specialized tissues are carried through blood to the whole body for

coordinating the actions of different organs .The former (neural mechanism ) is quick acting but shortlasting while the latter (hormonal mechanism ) is slow acting but long lasting .Hormones are also

found in plants which probably do not have the nervous system ; thus the hormonal system is the soleinternal regulator plants .

The nervous system plays a very important role in the regulation of hormones and the

hormones also influence the function of nervous system either directly or indirectly .Moreoverdifferent parts of the nervous system are now known to secrete some hormones called neuro-hormones.

PHYSIOLOGY OF HORMONESHormones are organic compounds that are produced from specialized cells and exert a regulatory

influence at a point remote from the site of secretion after being transported by issue fluid ; act likechemical messengers .

The rate of production of a given hormone is most commonly regulated by a homeostatic controlsystem , generally by negative feedback.

In higher animals including generate from the Endocrine Glands .Major Endocrine Glands are :

Sl.no. Name of the Gland Location /Seat ofthe Gland

Name of the secreted Hormone

1 Pineal Gland Brain Melatonin

2 Pituitary Gland Brain i) Growth Hormone(GH)ii) Adrenocorticotropic

Hormone(ACTH)iii) Thyroid Stimulating

Hormone (TSH)

3 Thyroid Gland Neck i) Trilodo Thyronine (T3)

ii) Thyroxine (T4)

4 Thymus Gland In between Neckand Chest

Unknown Function

5 Adrenal Gland Pyramid structureon the top of kidney

Cortisol

6 Genital Organs

Out of the above Melatonin and Cortisol have influence of light .


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RETINAL AND OCULAR PHYSILOGY

In the mammalian circadian system photic information is processed by the retina and relayed to thehypothalamus of the brain via a neural pathway called the Retino Hypothalamic Track

(RHT). The peak sensitivity of the circadian and neuroendrocrine system is near 500nm .

Experimentally it has been established that rhodospin or a rhodopsin based molecule is theprimary receptor for circadian and neuroendocrine regulation .

From other experimental data it suggests that other photo pigment might be involved in

regulatory effects . Studies also shown that bloodbrone elements circulating through the eye might beresponsible for transducing photic stimuli for circadian and neuroendrocrin regulation .

Neural pathway after retinal detection of photic information the RHT projects directly to

Suprachiasmatic Nucleus (SCN) , which serves as the primary central circadian oscillators /pacemaker which regulate daily rhythms such as the sleep wake cycle , body temperature rhythms and

24 hours secretary patterns of hormones .

By this pathway , the ambient light dark cycle entrains the rhythmic synthesis and secretion ofpineal melatonin . High level of melatonin are secreted during the night and low levels are secreted

during the day .

In the pineal gland melatyonin is synthesized and typically released into the circulation whenillumination diminishes and may help- explain why most of us sleep.

MELATONIN AND ITS EFFECT

Melatonin is a hormone secreted by the pineal gland that aids bio rhythm regulation .Biorhythm isdistributed by stress , crossing time zones and changing work shifts .

Melatonin secretion is enhanced in darkness and decreased by light exposure .As we age , melatoninproduction decreases .In addition to sleep , melatonin has many other functions.

Melatonin may influence human physiology , including the Sleep - wake cycle , in a timedependent manner via the bodys internal clock , Rapid eye movement (REM) sleep expression , is

strongly circadian modulated and the impact of REM sleep on primary brain functions ; metabolicprocesses and immune system function has becomes increasingly clear over the past decade .

Seasonal Affective Disorder (SAD) a depression occurring in winter months is associated withMelatonin secretion .

Pineal Melatonin has been shown in animals / humans to be involved in the regulation of Calciumand Phosphorus metabolism by stimulating the parathyroid glands and by inhibiting Calcitonin release

and prostaglandin ( a group of complex fatty acids present in the body that act as messengersubstances between cells .Effects includes stimulating the contraction of smooth muscle , regulating

production of stomach acid and modifying hormonal activity , excess causes arthritis )synthesis .External magnetic fields have been found to synchronise Melatonin secretion in experimental

animal and humans and may be beneficial in the treatment Osteoporosis .

During morning hours when melatonin levels begin to diminish , birds begin to sing and we also tendto wake up restored to start our daily activity .


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Functions :1) It lessens the effects of Jet Lag . Melatonin oral supplementation helps in hypertension

specifically for Pilots.

2) In laboratory studies Melatonin has been found to stimulate natural antioxidant systems inaddition to offering protection to DNA present within cells . It has an anti aging property .

3) It is also effective for treatment of Alzheimers disease , to reduce oxidative damage in sometypes of Parkinsons disease.

4) Melatonin may enhance the immune system . The details are not established in case of humansbut in cell culture and animal studies melatonin has immune stimulating capabilities.

5) It may have anti-tumor abilities. It s done is done in Italy (not in USA ) .

6) It can also alleviate certain forms of anxiety and depression .

7) It also has some smoothing effect on our genital organ due to suppression of system leads tovarious female diseases and male disorders .

8) Melatonin reduces body temperature .

9) Pineal melatonin has shown in animals to be involved in the regulation of Calcium andPhosphorus metabolism by stimulating the parathyroid glands and by inhibiting Calcitonin

release .

Other additional functions : Melatonin oral supplement has been found to reduce a) Night-time visit to toiletb) Reduce Night-time blood pressurec) Prevent migraine headachesd) Improve sleep of patiente) Irritable Bowl Syndrome


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CORTISOL

Cortisol is a hormone synthesized from Adrenal Gland. The amount of Cortisol present in theserum undergoes dinural variation with the highest rate of rise in the early morning , peaks at

noon and lower levels in the evening .Information about the light / dark cycle is transmitted from

the retina to the paired Suprechiasmatic nuclei (SCN) in hypothalamus .Changed patterns of theserum cortisol levels have been observed in connection with abnormal ACTH levels , clinicaldepression , psychological stress and such physiological stressors as hypoglycemia , illness ,

fever , trauma , surgery , fear ,pain , physical exertion or extreme temperature . There is alsosignificant individual variation , although a given person tends to have consistent rhythms .

Some effects of Cortisol being secreted into the blood stream are an increase in bloodpressure and glucose.

Elevated levels of melatonin during mania and elevated Cortisol levels during depression werethe principal findings .

BLUE LIGHT HAZARD

Light waves measuring approximately 400nm to 470nm in length are seen as the colour Blue.The blue bands of the visible light spectrum are adjacent to the invisible band of ultraviolet

(UV) light .It is divided into three wave lengths : UV-A , UV- B and UV-C .

The effects of UV- C are negligible as the waves are so short they are filtered by theatmosphere before reaching our eyes . UV-A and UV-B are responsible for damaging material ,

skin and eye with UV-B getting most of the blame .

Fluorescent lamp is a phosphor coated tube filled with Mercury and Argon vapour .Phosphors in lamps are rare earth compounds of various types that glow during absorption of

light radiation .The type and blend of phosphors used in the coating determine the colour ofemitted light.

Fluorescent lamp containing the older halophosphate type phosphors emits light that is high in

the blue spectrum . The phosphors increase the wave length of the invisibleUV rays are blocked mostly by the glass enclosure , protecting us to some extent from those

harmful wavelengths . The Blue light however passes through unimpeded .

Most Fluorescent lamps now use a Triphosphor mixture , based on Europium and Terbium ions, which more evenly distributes over the visible light spectrum . With a blend of phosphors

designed for a CCT of 5000 6500oK , theses lamps come close to imitating the colour of

daylight .


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PHOTO THERAPY

Photo therapy means treatment by light under medical supervision .It is regarded to be provenvalue in treatment of limited number of diseases .

A) SKIN DISEASES :1) Sun Tanning2) Psorasis3) Common Acne and Herpes4) Vitiligo

B) PHYCOLOGICAL / NEUROLOGICAL DISEASES

1) Depression2) Stress3) Heart rhythm4) Dream5) Alert Grade

C) TREATMENT OF METABOLIC CONDITIONS

1) Ricket2) Jaundice in new born babies

D) PHOTO CHEMOTHERAPY

1) Skin diseases under Sl. No. A(2 &3)2) Cancer

There are various methods of photo therapy .Few are discussed below :


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UV B - This type of treatment involves exposing the skin to UV light B . It is acommon , safe and very effective treatment , and generally works best when the

psoriasis layer are thin.

HOME PHOTOTHERAPY:

Patients who lives far from a doctor or whose schedule makes it difficult to go in forfrequent light treatments in a Doctor's office may purchase a home UVB unit and takethe therapy under medical prescription .

UV PHOTO THERAPY

It refers to the irradiation with short wave UV radiation .To treat the whole body , thepatient , undressed , stands in a specially designed cabinet containing fluorescent light

tube .

Some units offer narrow band UVB phototherapy (311nm).Increasing doses of UVB are given each exposure (three to five times weekly ), aiming

to turn the skin slightly pink . Sometimes uncomfortable sunburn will occur , at itsworst about 8 hours after treatment .This fades over the next few days and should be

treated with frequent and liberal emollient (comfortable) .

The effect of UVB is similar to Sun. Excessive exposure contributes toaging skin and to the skin cancers.

PSORIASIS

Psoriasis is a common inherited skin disorder which may vary considerably in extentand severity .UVB is usually suitable for most people with extensive psoriasis

.Although sometimes it worsen. It is not suitable for very fair skinned persons .Initially most patients have their treatment thre times a week. The first few

exposures will be short (les than 5 minutes ) .The length of exposure is graduallyincreased , according to the patient's response , upto a maximum of 30 minutes per

session .Few patients require such long exposures , most being controlled with shortertimes .

Most psoriasis patients will have their psoriasis cleared or much improve after 12 -24 treatments. At this stage treatments .At this stage treatments will usually be

discontinued .Even without treatment the skin may remain clear for some months.However the psoriasis may flare up again and further UVB treatment is necessary .

Those cases of psoriasis which appear to be resistant to UVB may still behelped by another form of UV treatment called PUVA.

DERMATITIS ( Eczyma)

UV - B is occasionally used for severe cases of Dermimatities .Frequency and dosagesof treatment is similar to that used for psoriasis .However , a course of photo therapy

may need to be more prolonged than that generally required for psoriasis .


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PHOTO CHEMOTHERAPY

It is defined as the combination of non ionizing Electromagnetic radiation and a drug tobring about a beneficial effect .Neither the drug alone nor the radiation along has any

significant biological activity .It is only the combination of drug and radiation that is

therapeutic .

PUVA ( Psoralen and UV )

It is a type of UV radiation treatment ( Photo therapy) used for severe skin diseases .PUIVA is combination treatment which consists of Psoralen (P) and then exposing the

skin to long wave UV -A radiation .

Psoralens are compounds found in many plants which makes the skin temporarilysensitive to UV-A . The ancient Egyptians were the first to invent it .

The number of exposure and the frequency of PUVA treatments will depend on the

condition being treated and the individual factors .

Methoxsalen capsules are taken two hours before exposure to UVA . Bulbsemitted different wavelengths are used for the UV .

Those patients required treatment to small areas only may be treated using the

small hand and foot units .

"Bathwater "PUVA may be suitable .In this case the hands and foot are soaked indilute solution of Methoxsalen for 30 minutes , then immediately exposed to UVA .

A few patients may be treated with topical Tripsor PUVA - a lotion painted on the effected areas 10

minutes before the exposure .Living cell systems absorbs energy from photons within the 320 - 400nm wave band , with a broad

peak of 340 - 360 nm , results in thymine ( It is a nitrogeneous based found in DNA) psorelen

photoproducts and the transient inhibition of DNA synthesis .

Side Effects : -- Burning like Sun burn like reaction ,

-- Itching-- Nausea

-- Cornea - cataract formation


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PHOTO DYNAMIC THERAPY

Photochemotherapy of Tuimours .

Photodynamic therapy employs visible radiation of a particular wavelength band as a catalyst in a

photo-degradation reaction .The products of this radiation are Cytotoxic , effectively destroy tumorcells .

The chemical Hematoprophyrin derivative (HpD) , when introduced into the blood , locates andbinds to tumor cells .

Exposure of the tumor to radiation at 630nm causes the production of Singlet Oxygen .Singlet oxygenis highly Cytotoxic and cosequently causes tumor cell degradation .

Filtered Xenon and Tungsten lamps can be used to treat cutaneous lesion . A pumped dye argon

LASER radiating at 630 nm , connected to an optical delivery system such as fibre optics can be usedwith an endoscope or similar device to reach internal cavities .

Photodynamic therapy has achieved partial or complete responses in 85 % of patients with lungs ,

Esophageal , bladder ,Ocular , head and neck , Neurological , and Gynecological tumors .Despite thissuccess treatment generally has been confined to cutaneous and subcutaneous tumors (including

Breast cancer , etc.).

The photo reactivity of HpD also can be empolyed in tumor loclization and detection , as radiation of400nm causes HpD to fluoresecene .

HpD is not toxic in the absence of light , however as the substance is retained in the skin , it can

causes photo sensitivity that may persist for 3 - 4 weeks after infusion .


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PHOTO THERAPY OF HYPERBILIRUBINEMIA ( Jaundice )

Hyperbilirubinimia occurs in infants ( 7 - 10%)when they are at 5 - 6 days . Jaundice results from the

accumulation of a yellow pigments bilirubin which is principally derived from the degradation ofhemoglobin .Infants do not have ability to get rid of those pigments through urine rather it goes on

increasing due to immaturity of liver. Peak levels of bilirubin reaches 5 - 13 mg /dL.

As the plasma concentration of bilirubin increases it can penetrate the blood brain barrier andaccumulate in brain which has some toxic infury to brain cells leads to develop neurological injury ,

including learning impairment , cerebral palsy , deafness and extreme case of death .


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Three methods of administered :

1) Conventional or overhead system of Fluorescent lamp .

2) Overhead Tungsten - Halogen spot light

3) A relati

Documents

Optical Radiation and Health Notes by KG Madam