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The EM Spectrum. Lesson 01: Dispersion Lesson 02/03: The EM Spectrum Lesson 04: Pupil Research Lesson 05: Pupil Presentations. EM Double and Triple Science Syllabus. The electromagnetic spectrum - PowerPoint PPT Presentation
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The EM SpectrumLesson 01: DispersionLesson 02/03: The EM SpectrumLesson 04: Pupil ResearchLesson 05: Pupil Presentations
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EM Double and Triple Science SyllabusThe electromagnetic spectrum understand that light is part of a continuous electromagnetic spectrum which includes radio,
microwave, infra-red, visible, ultraviolet, X-ray and gamma ray radiations and that all these waves travel at the same speed in free space
recall the order of the electromagnetic spectrum in decreasing wavelength and increasing frequency, including the colours of the visible spectrum
recall some of the uses of electromagnetic radiations, including radio waves: broadcasting and communications microwaves: cooking and satellite transmissions infra-red: heaters and night-vision equipment visible light: optical fibres and photography ultraviolet: fluorescent lamps X-rays: observing the internal structure of objects and materials and medical
applications gamma rays: sterilising food and medical equipment
recall the detrimental effects of excessive exposure of the human body to electromagnetic waves, including
microwaves : internal heating of body tissue infra-red : skin burns ultraviolet : damage to surface cells and blindness gamma rays : cancer, mutation
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Dispersion 24/04/23
Aim:• To be able to explain the cause of dispersion• To explain the nature of the electromagnetic
spectrum
Starter:
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DispersionThe white light ray is split into a spectrum of colours. This is known as DISPERSION.
The different colours of light have different wavelengths. Different wavelengths are refracted different amounts.
Red light is refracted least.
Violet light is refracted the most.
Which colour is refracted the most?How do you remember the order of the colours?Richard Of York Gave Battle In Vain
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Colour, Wavelength and Amplitude
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Newton’s Disk
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Dispersion Summary
Red/violetRefracted more/less
by glassLonger/shorter
wavelength
Red/violetRefracted more/less
by glassLonger/shorter
wavelength
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Addition of Colours There are three primary
colours: Red Blue Green
By adding together the primary colours you can make other colours. For example red and blue make green.
This is different to the reflection of light this is an optical illusion due to the way your eyes work.
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Colour Blindness No functioning cones:
See black and white, have problems with daylight, because it is too bright for them; they also lack visual acuity
One type of cone working: see colours only as variations in intensity, similar to black-and-
white or one colour images Red Cone Not Working:
typically only two (yellow, blue) can be distinguished - yellow comprises red, orange, yellow, and green, blue coincides with blue and purple
Green cone not working; green cannot be distinguished from certain combinations of red
and blue; this is the most common type of colour deficiency Blue cone not working:
longer wavelengths appear as red and the shorter ones as bluish-green; this colour deficiency is very rare
More than 8% of the male and about 0.04% of the female population have some sort of colour anomaly or deficiency.
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Tests
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Which is Longer?
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A Spiral?
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Definitions All Electromagnetic waves are energy waves They can travel through a vacuum They all travel at the speed of light (300 000 000
m/s) We group them by their properties and hence
uses, inside each group is a range of frequencies.
Copy
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Electromagnetic SpectrumRadio
Micro
Infra-RedLight
Ultra-Violet
X rays
Gamm
a Wavelength () increases
High frequencyShort wavelengthHigh energyMost penetrating
High frequencyShort wavelengthHigh energyMost penetrating
Low frequencyLong wavelengthLow energyLeast penetrating
Low frequencyLong wavelengthLow energyLeast penetrating
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The EM Spectrum recapAim:•To explain the dangers and uses of the EM Spectrum
Light, a type of radiation, is part of the electromagnetic spectrum.The electromagnetic spectrum is made up of different types of radiation.The different types of radiation have different properties and behaviour.All electromagnetic waves can travel through space.All electromagnetic waves travel at the same speed in a vacuum [300,000,000 m/s].
TRUE/FALSE
TRUE/FALSE
TRUE/FALSE
TRUE/FALSE
TRUE/FALSE
Starter:
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The Electromagnetic Spectrum 24/04/23
Aim:• To explain the uses and dangers of the EM Spectrum
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Electromagnetic SpectrumRadio
Micro
Infra-Red
Light
Ultra-Violet
X rays
Gamm
a Wavelength () increases
RememberMyInstructionsVisibleUnderX – RayGlasses
High frequencyShort wavelengthHigh energyMost penetrating
Low frequencyLong wavelengthLow energyLeast penetrating
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Uses and dangers of EM radiationCopy the Top of the following table into your books(we will fill it in as we go)
Radiation Uses DangersGammaX-rays
UltravioletLight
Infra redMicrowaves
Radio waves
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HighLevelnuclearwasteMicrobes can be
killed using gammaradiation
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Increasingdose tumour
view throughthe head
skull
healthybraintissue
Gamma rays can be used to treat brain tumours
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EM Radiation:
Uses:
Dangers:
sterilising surgical equipment and food, killing cancer cells.
High doses can kill cells. Lower does can cause cancer (brain, liver, bone, leukemia…)Sterility
Gamma
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X-raytube
Jumbo jet wings are regularly checked in this way to see if any micro-cracks have developed. These small cracks are too small to see any other way and could have fatal consequences.
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X-raytube
Detection of broken bones in the body
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Customs X-Rays are used to scan luggage in customs
Movie
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Damage to organs.X-rays can penetrateto the vital organs inside the body.
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EM Radiation:
Uses:
Dangers:
Shadow pictures of luggage and inside the human body.
High doses can kill cells. Lower doses can cause cancerSterility
X rays
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39637
UV
Visible light(longer wavelength)
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Outer dead skin cells Outer dead skin cells
Living skin cells Living skin cells
The effect of UV on cells
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EM Radiation:
Uses:
Dangers:
Sun beds, fluorescent lamps and security marking.
Sun Burn.Skin cancerBlindness
Ultraviolet
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Movie Shorter Wavelengths
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Optical Fibres
Optical fibres, that are used in communication, use total internal reflection.
What are the applications of total internal reflection?
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EM Radiation:
Uses:
Dangers:
Photography and endoscopes
Blindness
Light
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During the day the earth warms up as it absorbs short wave infrared rays from the sun
During the night the earth loses longer wavelength infrared rays by radiating them into space and the earth cools down.
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Too much water vapour and carbondioxide in theatmosphere willtrap the infraredrays and cause the earth to overheat
This effect iscalled thegreenhouseeffect (or globalwarming)
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How do infrared waves cook food?
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Night vision
All objects above absolute zero emit infrared radiation. The hotter an object is, the more heat radiation it emits. Some animals and cameras can detect infrared radiation and are able to build up a heat picture.
Which are the hottest/coolest parts of
the image shown?
light is hot
dark is cold
Fireman
Walking in the Woodland
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Uses of infrared – activity
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EM Radiation:
Uses:
Dangers:
Remote controls, radiant heaters, grills, optical fibre communication, night vision, Mobile Phones
Skin burns
Infrared
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Communications satellites use microwaves
The microwaves can pass straight through the ionosphere
Their shorter wavelength (higher frequency) means they are more penetrating than radio waves
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Microwave ovenYou will need to understand how microwaves cook foodThe microwaves have the exact wavelength(frequency) to be absorbed by the water moleculesThe molecules move fasterThe water temperatureincreases
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Demo DO NOT do this at Home
Beaker with water in the microwave Light Bulb in the beaker Heat for 5 seconds (until the light bulb lights)
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EM Radiation:
Uses:
Dangers:
Satellite communication, mobile phones, cooking, RADAR.
Internal tissue heating.
Microwaves
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Short wave radio and TV waves are broadcasted to line of sight aerials.
They cannot travel large distances because ofthe curvature of the earth.
aerial 1aerial 2
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Short wave radio and TV waves are broadcasted to line of sight aerials.
They cannot travel large distances because ofthe curvature of the earth.
transmitter
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Radio waves can reach the aerial if we usea charged layer in the atmosphere (theIONOSPHERE).
IONOSPHERE
The radio waves are reflected by this charged layerRemember that all types of light waves (electromagnetic radiation) can be reflected
aerial
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EM Radiation:
Uses:
Dangers:
Communication and astronomy.
Radio waves
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Movie Longer Wavelengths
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The electromagnetic spectrum
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Energy of electromagnetic waves
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Effect of electromagnetic waves
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EM Questions
1) Match up the following parts of the electromagnetic spectrum with their uses :
Gamma rays Allow us to see
Radio waves Remote Controls
Ultra Violet ‘See’ broken bones
Visible Carry TV signals
Microwaves RADAR
X rays Sterilise equipment
Infra Red Causes sun-tans
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EM Questions
2) Which radiations are missing from below?
Gamma A Ultraviolet Light Infrared B Radio waves
A. ___________
B. ___________
X raysMicrowaves
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Electromagnetic Spectrum
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Movie Uses of EM Spectrum
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The EM Spectrum recap
Aim:•To explain the dangers and uses of the EM Spectrum
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Research 24/04/23Aim:• Prepare a presentation on part of the EM
Spectrum
Task:• Groups of 2 or 3• Your presentation should last 3-4 minutes• Everyone must talk• You must explain at least the uses and
dangers
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Pupil Presentations 24/04/23Aim:• Make a presentation on your part of the EM
Spectrum
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