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P1b Revision Notes




J Wilkinson Page 1

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The Electromagnetic Spectrum

Electromagnetic radiation travels as waves. The waves carry energy.
Electromagnetic radiation can travel through a vacuum (space)



Wavelength and Amplitude of a Wave

wavelength


amplitude




Frequency of a Wave

How many waves pass by in 1 second.
Measured in Hz (Hertz)




e.g.
time = 0




time =…

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The Electromagnetic Spectrum
Type of Radiation Wavelength Frequency

Gamma radiation shortest Highest

X rays

Visible light

Infra red radiation

Microwaves

Radio waves Longest Lowest



Speed of Electromagnetic Waves

All electromagnetic waves travel at the same speed



wave speed (m/s) = frequency (Hz) x wavelength (m)

(if you need to use…

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Electromagnetic waves can be reflected off a substance or transmitted through it or absorbed by it.



Reflected:-




Transmitted:-




Absorbed:-




When electromagnetic waves are absorbed by an object the object heats up. The waves might cause an
alternating current in the substance.




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Can't get through thick
lead




Gamma Rays



Kill or damage
Can cause cancer
living cells.

Can also be used to kill
cancer cells.


Kill bacteria on food so it
stays fresh for longer

Sterilise surgical instruments
by killing microbes on them.




J Wilkinson Page 5

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Can damage living cells
and cause cancer

Stopped by thick
metal.




X rays




Absorbed by bones but not soft
tissue.




X ray pictures




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Security markers

Coating inside fluorescent tubes (write in ink that can only be seen
when ultra violet radiation shines on
it.)




Some substances absorb ultra
violet radiation and give out
visible light




Ultra violet radiation




From sun and sun beds.




Cause skin damage Cause eye damage, even
blindness
Sun
Tan…

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Eyes see different wavelengths as different



colours




Longest Lowest
red frequency
wavelength


orange




yellow




green
White light (from the Sun or a lamp)

is a mixture of all colours of light.
blue



indigo



violet Shortest Highest

wavelength frequency




Visible light


Given out by Sun, lamps etc.




Transmitted through optical fibres…

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Can burn the
Night vision cameras "see" infra
skin
Hotter objects give red
out more infra red
radiation
Used in radiant heaters,
toasters, grills.



Felt as heat




Given out by all objects




Infra red radiation




Remote controls send out infra red
Transmitted through
signals
optical fibres for
communication




J Wilkinson…

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Damage or
Microwave ovens kill body cells




Absorbed by water
molecules, heating the
water up




Microwaves



Communications




Mobile phone and satellite TV Signals to and from
Signals in mobile phone networks satellites
microwaves pass
through the
atmosphere




J Wilkinson Page 10

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