Optics ReviewOptics ReviewOptics ReviewOptics Review

Exam Review 2009Exam Review 2009

Optics Review: Types of Light Sources

• INCANDESCENT– Created by glowing objects– Give off lots of heat– Inefficient – cost more to operate– Cheap to make

• FLUORESCENT– Created by UV emission from mercury source– Less heat produced – Less expensive to run– More expensive to make

• PHOSPHORESCENT– Glow in the dark stickers, clocks etc.– Absorb light and then re-emit it later– Usually a greeny-yellow colour

• CHEMILUMINESCENT– Chemical reaction causes light– No heat– Glow sticks

• BIOLUMINESCENT– Chemiluminescence in living organisms– Fire flies, some deep sea fish

• Light travels in straight lines called RAYS

• Light is a form of energy and travels in WAVES

• “White” Light can be refracted into the VISIBLE SPECTRUM

ROY G. BIV

Optics Review: Properties of Light

• Primary Additive Colours• All colours can be made from 3 primary additive colours

of LIGHT

RED + BLUE + GREEN → WHITE

RED + BLUE → MAGENTARED + GREEN → YELLOWGREEN + BLUE → CYAN

Technologies that use this: TV’s, spotlights, movie theatres

THE HUMAN EYE!

Optics Review: Primary Colours of Light

Optics Review Primary Colours of Light

• Primary Subtractive Colours of Light• Take White light and subtract one primary colour and

we have a Subtractive ColourEx: White – blue = yellow

magenta + cyan → bluemagenta + yellow → redyellow + cyan → green

magenta + cyan + yellow → black

• These are used in pigments (paints, ink jet printer cartridges)

• Coloured filters pull (subtract) colours to produce desired results

Optics Review Primary Colours of Light

Example White – blue = yellowR + G + B – B = R + G

yellow + cyan → greenR + G + G +B → Green

*Green dominates the combination

Optics Review: EMR

• Electromagnetic Radiation is a spectrum of wave energies and includes VISIBLE light

• Waves have WAVELENGTH (), FREQUENCY(), and AMPLITUDE (A)

• From shortest to greatest frequency(least energy --------------------------------------------------------- most energy)

Radio – Micro – Infrared – VIS – UV – X-Rays – Gamma Rays

Longest ----------------------------------------------- shortest

Optics Review: Uses of EMR

• RadioWaves – TV, radio, cell phones

• Microwaves– Microwave ovens – cooking food– Telecommunications

• Infrared– Remote controls– Thermal imaging

• UV– Tanning (also causes sun burns and skin

damage)– Heating lamps – fast food, spas

• X-Rays– Doctors and dentists use to see bones/teeth

• Gamma Rays– Doctors use to target and kill cancer cells

• Light travels in straight lines called RAYS

• Light bounces or reflects off of hard, shiny surfaces like a mirror

• Law 1: The Angle of Incidence (i) = the Angle of Reflection (r)

• Law 2: The Incident Ray (IR), Reflected Ray (RR), and the Normal (N) are in the same plane

Optics Review: Laws of Reflection

IR RRi r

N

Reflecting Surface

• Example: If the angle of incidence is 45o, what is the angle of reflection?

• Law of Reflection states that i = r so both equal 45o

• NOTE: i is between the Incident Ray and the Normal

Optics Review: Laws of Reflection

IR RR45 r

N

Mirror

• Light “bends” or refracts when light moves at an angle from one medium to another

• Law 1: The refracted ray bends towards the normal if light enters a denser medium (air → water)

• Law 2: The refracted ray bends away from the normal if light enters a less dens medium (water → air)

Optics Review: Laws of Refraction

IR

N

• When light enters water, light is “bent”• This causes optical illusions• Double images• Images of objects where they are not

• REFRACTION and REFLECTION ALSO CAUSE:• Rainbows• Sun dogs (rainbow like circles around the sun on the

very cold days)• Sunsets and Sunrises – dust and oxygen and nitrogen

particles in the air reflect and refract light• BLUE SKY – oxygen and nitrogen scatter (reflect)

light filtering out colours other than blue

Optics Review: Refraction

Optics Review: Properties of Lenses

• Lenses are shaped pieces of plastic or glass that refract light

• Convex Lenses: thicker in middle – converge or focus light

• Concave Lenses: thicker on edge – diverge or spread light

• Convex lenses can • Magnify• Invert• Form real images • Concave lenses can:• Minimize• Create inverted or upright images

Optics Review: Properties of Lenses

Optics Review: Properties of Mirrors

• Lenses are shaped pieces of plastic or glass that refract light

• Convex Mirrors (fisheye): Create virtual, upright, smaller images

• Used in side mirrors, security mirrors• Concave Lenses: can create many different types

of images depending upon placement• Used for vanity/makeup mirrors - magnifying

Optics Review: The EYE

• The eye is the organ responsible for sight • The retina has two types of cells:

• RODS – sensitive to light• See in shades of gray

• CONES – sensitive to colour• RED, GREEN & BLUE (the three primary colours)

Optics Review: The EYE

Optics Review: The EYE

Optics Review: The EYE

• The EYE

• Eyelash• Retina• Lens• iris• Ciliary muscles• Optic Nerve

• The Camera• Lens cap• Film / chip• Lens• Diaphragm• Focus ring• USB cable

Optics Review: The EYE and Lenses

• Farsightedness – lens too flat, the image produced by the lens is too far past the retina

• Correction – use a convex lens to converge the image on the retina

Optics Review: The EYE and Lenses

• Nearsightedness – lens too curved; the image produced by the lens is too far forward of the retina

• Correction – use a concave lens to diverge the image on the retina

Optics Review: The EYE and Lenses