Wave features
Amplitude
The amplitude of a wave is the maximum distance from the undisturbed position.
Wavelength 位
The wavelength of a wave is the distance between a point on one wave and the same point on the next wave.
It is often easiest to measure this from the The bottommost point of a wave. of one wave to the trough of the next wave, or from theThe topmost part of a wave. of one wave to the crest of the next wave.
But it doesn't matter where you measure it - as long as it is the same point on each wave.
The symbol for wavelength is the Greek letter lambda, 位.
Wavelength is a distance so it is measured in m.
Frequency f
The frequency of a wave is the number of waves produced by a source each second.
It is also the number of waves that pass a certain point each second.
The unit of frequency is the hertz (Hz).
It is common for kilohertz (kHz), megahertz (MHz) and gigahertz (GHz) to be used when waves have very high frequencies.
For example:
- most people cannot hear a high-pitched sound above 20 kHz (20 kHz = 20,000 Hz);
- radio stations broadcast radio waves with frequencies of about 100 MHz (100 MHz = 100,000,000 Hz);
- most wireless computer networks operate at 2.4 GHz (2.4 GHz = 2,400,000,000 Hz).
Remember:
- kilo k = 1000 or 103;
- mega M = 1,000,000 or 106;
- giga G = 1,000,000,000 or 109.
The frequency of a wave can be calculated using the equation:
\(\text{frequency f =}~\frac{\text{number of waves to pass a point}}{\text{time taken in seconds}}\)
Example
6 waves pass a boat on the sea in 10 seconds.
What is the frequency of the waves?
Answer
\(\text{frequency f =}~\frac{\text{number of waves to pass a point}}{\text{time taken in seconds}}\)
\(\text{frequency f =}~\frac{6}{10}\)
\(\text{frequency f =}~{0.6~Hz}\)
The frequency of the waves is \(\text{0.6}{~Hz}\)