A-Level Physics - Waves

Waves intro

There are many ways to categorise waves; electromagnetic waves, mechanical waves, progressive waves, standing waves, transverse, longitudinal, polarised, unpolarised, etc

Each classification involves different waves from different categories

In this spec, you look specifically at classifying waves as progressive or stationary

What is the general definition for a wave?

Waves are oscillations of the particles of a medium

What is a progressive wave?

A progressive wave carries energy from one place to another without transferring any material

Therefore, what do waves cause?

Waves cause the particles of the medium they are travelling through to osciallte

What causes waves?

Waves are caused by something making particles or fields (e.g. electric or magnetic fields) oscillate at a source

These oscillations pass through the medium or field as the wave travels, carrying energy with it

A wave transfers this energy away from tis source, so the source of the wave loses energy

How can you identify if a wave is carrying energy?

• EM waves cause things to heat up

• X-Rays and gamma rays knock electrons out of their orbits, causing ionisation

• Loud sounds cause large oscillations of air particles which can make things vibrate

• Wave power can be used to generate electricity

What things can happen to a wave?

• Reflection

• Refraction

• Diffraction

• Exhibit inteference

• Be polarised (in the case of transverse waves)

What is reflection?

When a wave is bounced back when it hits a boundary (e.g. you can see the reflection of light in mirrors)

What is refraction?

When a wave changes direction as it enters a different medium. The change in direction is a result of the wave slowing down or speeding up.

What is diffraction?

When a wave spreads out as it passes through a gap or round an obstacle e.g. you can hear sound from round a corner

What is the displacement (x) of a wave?

How far a point on the wave has moved from its undisturbed position

What is the amplitude (A) of a wave?

The maximum magnitude of the displacement (i.e. the distance from the undisturbed position to the peak / trough)

What is the wavelength () of a wave?

The length of one whole wave oscillation or wave cycle (e.g the distance between two peaks of a wave)

What is the period (T) of a wave?

• The time taken for one whole wave cycle

What is the frequency (f) of a wave?

The number of whole wave cycles (oscillations) per second passing a given point, or the number of whole wave cycles (oscillations) given out from a source per second

What is the phase of a wave?

A measurement of the position of a certain point along the wave cycle

What is phase difference?

A measurement of how far out of step the oscillations are