The electromagnetic spectrum table
This table is nearly all you need to know about the e-m spectrum on one page.
The electromagnetic spectrum
Print or copy it out if you want a permanent summary.
Check your syllabus to see if there are particular examples or applications you need to know about in detail. This summary should give you some useful background ideas and information.
Amplitude, Wavelength, Frequency, and Speed
The amplitude (a) is the total distance betweeen the crest of a wave and the centre line. It's a distance, so can be measured in metres, centimetres, millimetres or smaller units of length.
The wavelength (l) is the distance between one peak of the wave and the next peak. It's a distance so can be measured in metres, centimetres etc. It is sometimes given the Greek letter (lambda). It's also the distance between one part of the wave and the next part which is at exactly the same stage of vibration - but 'peak-to-peak' is easier to remember.
The frequency (f) is the number of complete waves passing a point each second. It's a 'number per second' so it's measured in /s or s-1; usually called hertz (Hz) after a German physicist.
1 kilohertz = 1 kHz = 1000 Hz
1 megahertz = 1 MHz = 1,000,000 Hz
For example:
100 complete sound waves enter your ear in a second (you'd hear a deep hum).
f = 100 per second
= 100 /s = 100 s-1
= 100Hz
The speed of a wave (v) is just what it says. It's the speed at which the vibrations in the wave move from one point to the next. Wave speed is measured in metres per second (m/s, ms-1).
For example:
speed of sound in air = 330 m/s (approximate)
speed of light in space = 300,000,000 m/s
Print out or copy this page if you want a basic revision sheet. You may want to check out the next section first.
