e.m.waves

Stopwatch Graph Home

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


Dispersion 01/05/23

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


Dispersion Summary

Red/violetRefracted more/less

by glassLonger/shorter

wavelength

Red/violetRefracted more/less

by glassLonger/shorter

wavelength


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-Red

Light

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 01/05/23

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

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


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


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


Microwave ovenThe microwaves have the exact wavelength(frequency) to be absorbed by the water moleculesThe molecules move faster

The water temperatureincreases


EM Radiation:

Uses:

Dangers:

Satellite communication, mobile phones, cooking, RADAR.

Internal tissue heating.

Microwaves


EM Radiation:

Uses:

Dangers: None is found

Communication and astronomy.

Radio waves


The electromagnetic spectrum


Energy of electromagnetic waves


Effect of electromagnetic waves


EM Questions1) 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 Communications

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

e.m.waves

Education