What is the unit of wavelength

What is the unit of wavelength?

You need to know about these quantities used in waves – what they mean, the symbols used for them and the units used to measure them.

Diagram showing the amplitude of a wave with its crests and troughs.

The amplitudea, of a wave is the distance from the center line (or the still position) to the top of a crest or to the bottom of a trough. Be careful with this quantity – the center line is not always given in a diagram. Amplitude is measured in meters (m). The greater the amplitude of a wave then the more energy it is carrying.

The wavelengthλ, of a wave is the distance from any point on one wave to the same point on the next wave along. (The symbol is a Greek letter, ‘lambda’.) To avoid confusion, it is best to measure wavelength from the top of a crest to the top of the next crest, or from the bottom of a trough to the bottom of the next trough. Wavelength is also measured in meters (m) – it is a length after all.

The frequencyf, of a wave is the number of waves passing a point in a certain time. We normally use a time of one second, so this gives frequency the unit hertz (Hz), since one hertz is equal to one wave per second.

Don’t get confused with this quantity-frequency. It is not a distance traveled by waves, nor is it a speed, although it is linked to both of these quantities. For water waves and sound waves, the unit hertz is usually good enough but radio and TV waves have such a high frequency that the kilohertz (kHz) or even the megahertz (MHz) are better units.

    • 1 kHz = 1,000 Hz
    • 1 MHz = 1,000,000 Hz

The speed (or sometimes you might see it called velocity) of a wave, v, is how far the wave travels in a certain time.

Wave speed is measured in meters per second (m/s).

All the electromagnetic waves travel at 300,000,000 metres per second (3 x 108 m/s). Sound travels at about 340 meters per second.


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