Physics GCSE: Properties of Waves

Revision Summary

Frequency, wavelength, amplitude and time period are used to describe waves.

Waves can be transverse or longitudinal.

Transverse waves - the vibration is at right angles to the wave motion, e.g. light, water waves and the electromagnetic spectrum waves.

Longitudinal waves - the vibration is parallel to the wave motion, e.g. sound and some earthquake waves.

Wave Speed (m/s) = Frequency (Hz) x wavelength (m)

Reflection is the bouncing of waves off a surface. There are three rules of reflection that you need to know.

1. The angle of incidence always equals the angle or reflection.
   
   
2. The distance from the object to mirror is the same as the distance from the mirror to the image.
   
   
3. The image is always the same size as the object but is laterally inverted.
   
   

Refraction is the bending of a wave when it goes from one substance into another. Refraction happens because the speed and wavelength of the wave changes as the wave goes into the other substance. The frequency of the wave stays the same.

Total internal reflection happens when the angle of incidence, of a wave going from a substance into air, is greater than the critical angle. The wave bounces off the boundary, obeying the rules of reflection.

Dispersion of white light produces a spectrum. This is caused by refraction. Light of different frequencies is refracted by different amounts. Red is refracted the least and violet the most. This causes white light to be split up into seperate colours.

Diffraction is the spreading out of a wave as it goes through a gap, or around an object. The smaller the gap or the larger the wavelength the greater the diffraction.

Diffraction is most effective when the size of the gap is approximately the same as the wavelength of the wave.

You will need to be able to draw diagrams showing how waves reflect, refract and diffract.