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E-quations: waves
A wave is a means of transferring energy between two points. Here the energy Cris uses to swing his arm, travels as a wave along the rope, and moves the ball at the other end.
What are waves?
- A wave is a periodic disturbance which travels through space. Periodic means the shape or pattern repeats itself at regular intervals.
- There are many types of waves, such as water waves, sound waves, light waves.
- Waves can travel through matter - often the matter (or medium) oscillates to produce the wave.
- Only the shape of the wave travels, not the medium.
- Light waves are a bit different - they are made up of electric and magnetic fields.
- As it travels, the wave transfers energy from one place to another.
Describing waves
To study waves we need ways to describe them. The good thing about waves is that, no matter what type of wave you are dealing with, you can use the same basic terms and definitions:
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Wavelength ( |
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Wavelength is often measured from maximum to maximum (left), but it can also be from minimum to minimum (middle), or between any two points that are in phase (right). |
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) is the distance before the wave repeats.
It is measured between any two points that are in phase (at the same stage in the repeat cycle).
) is the size of the oscillation - the maximum displacement from the equilibrium position.
) of waves on the sea surface. This is the distance between the crest (top) of a wave and the trough (lowest point).
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The period (
The frequency (
The wave velocity ( |
In one wave period a full wavelength travels past a fixed point in space.
At the end of this period the first maximum has reached the original position of the second maximum, and the wave has travelled a distance equal to one wavlength.
This means the speed of the wave is one wavelength per wave period; in other words
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) of a wave is the time it takes to repeat.
) is the number of repeats made in one second. As you can see frequency and period are related by 
) is the speed at which the wave travels. A wave that takes T seconds to travel past a point in space travels at the velocity 
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Last update: 19 January 2009 |
Contact: o4s@noc.soton.ac.uk |