They transfer the energy locked up in the vibrations.
Waves have a measurable speed, wavelength and frequency.
Waves meeting a boundary between mediums may be reflected, refracted or absorbed - often a mixture of all three.
Waves passing through a gap may be diffracted (spread) - the spreading is only noticeable if the gap is similar to the wavelength.
Electromagnetic waves carry transverse vibrations in electrical and magnetic fields, not vibrating particles.
E-m waves don't need matter to travel through - they can travel through empty space (a vacuum).
In a vacuum, all e-m waves travel at (approximately) 300 million metres per second (3 x 108m/s) - the fastest speed in the universe.
When e-m waves travel through matter (for example, light through air or glass), they travel a bit slower than this but rarely less than half as fast as in vacuum.
Waves of different frequencies travel at different speeds in transparent matter - so a mixture of waves can be separated out by diffraction. For example, white light is split up into a mixture of colours when it goes through a prism.
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The electromagnetic spectrum table
This table is nearly all you need to know about the e-m spectrum on one page.
The electromagnetic spectrum
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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
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