Physics - 13 Electromagnetic Waves - 13.1 The Electromagnetic Spectrum & 13.2 Light, Infrared, Microwaves and Radio Waves

Electromagnetic wave

transverse waves that transfer energy from a source to an absorber

Electromagnetic spectrum order

- radio waves

- microwaves

- infrared

- visible light

- ultraviolet radiation

- x-rays

- gamma radiation

Electromagnetic spectrum acronym

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Speed of electromagnetic waves

300,000,000 m/s

wave speed =

frequency x wavelength

v =

fλ

As frequency increases, energy...

increases

As wavelength decreases, energy...

increases

Wavelengths of visible light

400nm - 700nm

Maximum wavelength of radio waves

10000m

Minimum wavelength of x-rays and gamma rays

10⁻¹⁵

White light

light with all the colours of the visible spectrum

Sunlight

imperfect white light; some frequencies are lost as energy is absorbed by chemicals in the sun's atmosphere

Long-wavelength visible light

red

Short-wavelength visible light

violet

Effect of infrared radiation on living cells [3]

- damage

- burn

- kill

Incandescence

process that releases light with heat

What affects how much infrared radiation an object emits?

its temperature

Uses of infrared radiation [5]:

- optical fibres

- remote control handsets

- infrared scanners

- night vision

- heating objects quickly

Uses of infrared radiation: optical fibres

infrared radiation is absorbed less than visible light in glass fibres

Uses of infrared radiation: remote control handsets

a sequence of infrared pulses are sent out and detected electronically

Uses of infrared radiation: infrared scanners

detect hot areas on the body that could indicate unhealthy tissue

Uses of infrared radiation: night vision

used to see people or animals in the dark

Uses of infrared radiation: heating objects quickly

used to warm rooms quickly or heat up food

Uses of microwaves [2]:

- satellite/long-distance communications

- microwave ovens

Uses of microwaves: satellite communications

can penetrate the atmosphere and carry signals from Earth to satellites and vice versa

Uses of microwaves: microwave ovens

can penetrate food and are absorbed by water, fat and sugar molecules in food, heating it

Uses of radio waves [4]:

- FM & AM radio

- television

- cell phones

- MRI scans

CCD

Charged Coupled Device

Dangers of radio & gamma waves

penetrate the body and may cause internal heating

Earth's atmosphere blocks out [5]:

- gamma

- x-ray

- ultraviolet

- most infrared

- low frequency radio

Earth's atmosphere is penetrated by [3]:

- almost all visible light

- most radio waves

- most microwaves