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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

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the em spectrum

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
EM Double and Triple Science Syllabus

The 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 20 08 2014
Dispersion20/08/2014
  • Aim:
  • To be able to explain the cause of dispersion
  • To explain the nature of the electromagnetic spectrum

Starter:

dispersion
Dispersion

The 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.

Richard Of York Gave Battle In Vain

How do you remember the order of the colours?

Which colour is refracted the most?

Red light is refracted least.

Violet light is refracted the most.

dispersion summary
Dispersion Summary

Red/violet

Refracted more/less by glass

Longer/shorter wavelength

Red/violet

Refracted more/less by glass

Longer/shorter wavelength

addition of colours
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
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.
definitions
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

slide21

Radio

Micro

Infra-Red

Light

Ultra-Violet

X rays

Gamma

Electromagnetic Spectrum

Wavelength () increases

Low frequency

Long wavelength

Low energy

Least penetrating

High frequency

Short wavelength

High energy

Most penetrating

High frequency

Short wavelength

High energy

Most penetrating

Low frequency

Long wavelength

Low energy

Least penetrating

the em spectrum recap
The EM Spectrum recap
  • Aim:
  • To explain the dangers and uses of the EM Spectrum

Starter:

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

the electromagnetic spectrum 20 08 2014
The Electromagnetic Spectrum20/08/2014
  • Aim:
  • To explain the uses and dangers of the EM Spectrum
slide24

Radio

Micro

Infra-Red

Light

Ultra-Violet

X rays

Gamma

Electromagnetic Spectrum

Wavelength () increases

High frequency

Short wavelength

High energy

Most penetrating

Low frequency

Long wavelength

Low energy

Least penetrating

Remember

My

Instructions

Visible

Under

X – Ray

Glasses

uses and dangers of em radiation
Uses and dangers of EM radiation

Copy the Top of the following table into your books

(we will fill it in as we go)

slide27

High

Level

nuclear

waste

Microbes can be

killed using gamma

radiation

slide28

Increasing

dose

tumour

healthy

brain

tissue

view through

the head

Gamma rays can be used to treat brain tumours

skull

em radiation uses dangers
EM Radiation:Uses:Dangers:

Gamma

sterilising surgical equipment and food, killing cancer cells.

High doses can kill cells.

Lower does can cause cancer (brain, liver, bone, leukemia…)

Sterility

slide31

X-ray

tube

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.

slide32

X-ray

tube

Detection of broken

bones in the body

customs
Customs
  • X-Rays are used to scan luggage in customs
  • Movie
slide34

Damage to organs.

X-rays can penetrate

to the vital organs

inside the body.

em radiation uses dangers1
EM Radiation:Uses:Dangers:

X rays

Shadow pictures of luggage and inside the human body.

High doses can kill cells. Lower doses can cause cancer

Sterility

slide37

UV

39637

Visible light

(longer wavelength)

slide39

The effect of UV on cells

Outer dead skin cells

Outer dead skin cells

Living skin cells

Living skin cells

em radiation uses dangers2
EM Radiation:Uses:Dangers:

Ultraviolet

Sun beds, fluorescent lamps and security marking.

Sun Burn.

Skin cancer

Blindness

slide43

Optical Fibres

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

What are the applications of total internal reflection?

em radiation uses dangers3
EM Radiation:Uses:Dangers:

Light

Photography and endoscopes

Blindness

slide46

During the night the earth

loses longer wavelength

infrared rays by

radiating them

into space

and the earth

cools down.

During the day

the earth warms

up as it absorbs

short wave

infrared rays

from the sun

slide47

This effect is

called the

greenhouse

effect

(or global

warming)

Too much water

vapour and carbon

dioxide in the

atmosphere will

trap the infrared

rays and cause

the earth to overheat

night vision
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

Walking in the Woodland

Fireman

dark is cold

em radiation uses dangers4
EM Radiation:Uses:Dangers:

Infrared

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

Skin burns

slide53

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

slide54

Microwave oven

You will need to understand how microwaves

cook food

The microwaves have the exact wavelength

(frequency) to be absorbed by the water

molecules

The molecules move faster

The water temperature

increases

slide55
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 dangers5
EM Radiation:Uses:Dangers:

Microwaves

Satellite communication, mobile phones, cooking, RADAR.

Internal tissue heating.

slide58

Short wave radio and TV waves are

broadcasted to line of sight aerials.

They cannot travel large distances because of

the curvature of the earth.

aerial 1

aerial 2

slide59

Short wave radio and TV waves are

broadcasted to line of sight aerials.

They cannot travel large distances because of

the curvature of the earth.

transmitter

slide60

Radio waves can reach the aerial if we use

a charged layer in the atmosphere (the

IONOSPHERE).

IONOSPHERE

The radio waves are reflected by this charged

layer

Remember that all types of light waves

(electromagnetic radiation) can be reflected

aerial

em radiation uses dangers6
EM Radiation:Uses:Dangers:

Radio waves

Communication and astronomy.

slide67

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
EM Questions

2) Which radiations are missing from below?

Gamma

A

Ultraviolet

Light

Infrared

B

Radio waves

  • ___________
  • ___________

X rays

Microwaves

the em spectrum recap1
The EM Spectrumrecap
  • Aim:
  • To explain the dangers and uses of the EM Spectrum
research 20 08 2014
Research20/08/2014
  • Aim:
  • 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 20 08 2014
Pupil Presentations20/08/2014
  • Aim:
  • Make a presentation on your part of the EM Spectrum
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