The electromagnetic spectrum · revision map · IGCSE 0625, Topic 3.3
TOPIC 3.3 · THE ELECTROMAGNETIC SPECTRUM
CAMBRIDGE IGCSE PHYSICS 0625 · ONE-PAGE REVISION MAP
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EM
SPECTRUM3.3
SPECTRUM3.3
All EM Waves Share
A family of transverse waves that carry energy. They all travel at the same speed in a vacuum and differ only in wavelength and frequency.
Key Facts
The wave speed links to frequency and wavelength.
v = f λ
v = speed, f = frequency,
λ = wavelength
λ = wavelength
c = 3 ×10&sup8; m/s
the speed of all EM
waves in a vacuum
waves in a vacuum
The Spectrum · Low to High Frequency
In order of increasing frequency (decreasing wavelength): Radio, Microwave, Infrared, Visible, Ultraviolet, X-ray, Gamma.
Uses of Each Region
- Radio: TV and radio broadcasting, communications.
- Microwave: satellite links, mobile phones, Wi-Fi, cooking food.
- Infrared: remote controls, thermal imaging, heaters, fibre optics.
- Visible: human vision, photography, illumination.
- Ultraviolet: fluorescent lamps, security marking, sterilising, tanning.
- X-rays: imaging bones, airport security.
- Gamma: sterilising tools, treating cancer.
Harmful Effects
Higher-frequency waves carry more energy and do more damage to the body.
- Microwaves: internal heating of body tissue.
- Infrared: skin burns.
- Ultraviolet: skin cancer, eye damage, premature ageing.
- X-rays and gamma: ionising, so they cause cell mutation and cancer.
Digital vs Analogue SignalsEXTENDED
An analogue signal varies continuously; a digital signal is a stream of pulses, on or off (1 or 0).
- Both pick up noise and weaken over distance.
- Digital noise is removed and the signal is regenerated cleanly; it carries more information at higher quality and is easy to process, store and encrypt.