Properties of waves

Waves transfer energy from one place to another without transferring matter, sort of like a mexican wave.

A spring can be used to show the movement of waves

If you move one end of a spring up and down you can see the wave moving to the other end.

This is a transverse wave, particles of the medium oscillate perpendicularly to the direction of the energy transfer.

If you push the spring in and out you get a longditudinal wave, as the particles of the medium oscillate parallel to the dicrection of the energy transfer.

The period of the wave is how long it takes for it to complete one full oscillation.

It is calculated using: Period (s) = 1 (number of oscillations)/frequency

Frequency is the number of oscillations per second

It is calculated using: Frequency (Hz) = 1 (number of oscillations)/period

Wavelength and amplitude are also important measurements for waves (measured in metres).

• Amplitude is the largest distance from the equilibrium position to a point on a wave
• Wavelength is the distance between two neighbouring wavefronts, so in transverse waves the distance between crests.

You also need to know the equation involving wavelength and frequency:

wave speed = frequency x wavelength

• Water waves can be set up in a Ripple Tank, where a rod at one end of a tank of water creates a series of ripples.
• A bright light shone through the water onto a sheet of paper shows the ripples on the water very clearly as a series of parallel lines travelling along with constant speed.
• These parallel lines are the peaks of the ripples on the water. We call them wavefronts.

The Doppler effect describes the phenomenon of the observed wavelength and frequency of waves changing when the source of the waves is moving with respect to an observer.

This applies to any type of wave.

The wavelength and frequency don't actually change.

• When the source of the waves is approaching the frequency shifts upwards for observers.
• When the source of the waves is receding, the frequency shifts downwards for observers

Example: when an ambulance goes past the pitch decreases as it goes further away

All waves can be reflected or refracted.

• Reflection happens when a wave hits a plane and bounces off

• A wave's speed can change when moving from one medium to another if the wave crosses the medium at an angle.
• The change in speed will cause the direction of the wave's motion to change and it will appear to bend.
• This is refraction.