The EM Spectrum

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The EM SpectrumLesson 01: DispersionLesson 02/03: The EM SpectrumLesson 04: Pupil ResearchLesson 05: Pupil Presentations


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


Dispersion 24/04/23

Aim:• To be able to explain the cause of dispersion• To explain the nature of the electromagnetic

spectrum

Starter:


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


Colour, Wavelength and Amplitude


Newton’s Disk


Dispersion Summary

Red/violetRefracted more/less

by glassLonger/shorter

wavelength

Red/violetRefracted more/less

by glassLonger/shorter

wavelength


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.


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.


Tests


Which is Longer?


A Spiral?


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


Electromagnetic SpectrumRadio

Micro

Infra-RedLight

Ultra-Violet

X rays

Gamm

a Wavelength () increases

High frequencyShort wavelengthHigh energyMost penetrating


Low frequencyLong wavelengthLow energyLeast penetrating



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:


The Electromagnetic Spectrum 24/04/23

Aim:• To explain the uses and dangers of the EM Spectrum


Electromagnetic SpectrumRadio

Micro

Infra-Red

Light

Ultra-Violet

X rays

Gamm

a Wavelength () increases

RememberMyInstructionsVisibleUnderX – RayGlasses




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


HighLevelnuclearwasteMicrobes can be

killed using gammaradiation


Increasingdose tumour

view throughthe head

skull

healthybraintissue

Gamma rays can be used to treat brain tumours


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


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.


X-raytube

Detection of broken bones in the body


Customs X-Rays are used to scan luggage in customs

Movie


Damage to organs.X-rays can penetrateto the vital organs inside the body.


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


39637

UV

Visible light(longer wavelength)

Stopwatch Graph HomeMovie Friends


Outer dead skin cells Outer dead skin cells

Living skin cells Living skin cells

The effect of UV on cells


EM Radiation:

Uses:

Dangers:

Sun beds, fluorescent lamps and security marking.

Sun Burn.Skin cancerBlindness

Ultraviolet


Movie Shorter Wavelengths


Optical Fibres

Optical fibres, that are used in communication, use total internal reflection.

What are the applications of total internal reflection?


EM Radiation:

Uses:

Dangers:

Photography and endoscopes

Blindness

Light


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.


Too much water vapour and carbondioxide in theatmosphere willtrap the infraredrays and cause the earth to overheat

This effect iscalled thegreenhouseeffect (or globalwarming)


How do infrared waves cook food?


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


Uses of infrared – activity


EM Radiation:

Uses:

Dangers:

Remote controls, radiant heaters, grills, optical fibre communication, night vision, Mobile Phones

Skin burns

Infrared


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


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


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)


EM Radiation:

Uses:

Dangers:

Satellite communication, mobile phones, cooking, RADAR.

Internal tissue heating.

Microwaves


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


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


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


EM Radiation:

Uses:

Dangers:

Communication and astronomy.

Radio waves


Movie Longer Wavelengths


The electromagnetic spectrum


Energy of electromagnetic waves


Effect of electromagnetic waves


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


EM Questions

2) Which radiations are missing from below?

Gamma A Ultraviolet Light Infrared B Radio waves

A. ___________

B. ___________

X raysMicrowaves


Electromagnetic Spectrum


Movie Uses of EM Spectrum


The EM Spectrum recap

Aim:•To explain the dangers and uses of the EM Spectrum


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


Pupil Presentations 24/04/23Aim:• Make a presentation on your part of the EM

Spectrum

The EM Spectrum

Documents

Transcript of The EM Spectrum