Summary AQA GCSE triple higher physics study notes key topic 6

Physics – Key Topic 6
4.6 Waves
4.6.1 Waves in air, fluids and solids
4.6.1.1 Transverse and longitudinal waves
 Waves transfer energy and information from one place to another without
transferring matter
- When waves travel through a medium, the particles of the medium oscillate and
transfer energy between each other
 Waves may either be transverse or longitudinal
 Transverse waves:
- To measure the speed of ripples on a water surface, count the number of waves
passing at a point in time, then use the wave speed equation
- Transverse waves have oscillations perpendicular to the direction of energy
transfer
- Ripples on a water surface, light waves, electromagnetic waves
 Longitudinal waves show areas of compression and rarefaction. Sound waves
travelling through the air are longitudinal
- they have oscillations parallel to the direction of energy transfer
 By attaching a signal generator to a speaker you can generate sounds with a specific
frequency.
- set up the oscilloscope so the detected waves at each microphone are shown as
separate
- start with both microphones next to the speaker, then slowly move one away until
the two waves are aligned on the display, but have moved exactly one wavelength
apart
- measure the distance between the microphones to find one wavelength
- you can then use the formula to find the speed of the sound waves passing through
air

4.6.1.2 Properties of waves

,  The amplitude of a wave is the maximum displacement of a point on a wave away
from its undisturbed position – the height of a wave above the equilibrium line
- Equilibrium line is the line if the wave flattened out
 The wavelength of a wave is the distance from a point on one wave to the equivalent
point on the adjacent wave
 The frequency of a wave is the number of waves passing a point each second
 Frequency (Hz) = 1/time period (s)
 Oscillation is a repeated action back and forth or up and down
 A period is the time is takes for one complete wave to pass
 The wave speed is the speed at which the energy is transferred through the medium
 All waves obey the wave equation:
 Wave speed (m/s) = frequency (Hz) x wavelength (m)

4.6.1.3 Reflection of waves
 Waves can be absorbed, transmitted or reflected at the boundary between two
different materials
- the waves are absorbed by the material the wave is trying to cross into – this
transfers energy to the material’s energy stores
- the waves are transmitted – the waves carry on travelling through the new material.
This often leads to refraction
- the waves are reflected
- what happens depends on the wavelength of the wave and the properties of the
material
 Angle of incidence = angle of reflection
 The angle of incidence is the angle between the incoming wave and the normal. The
angle of reflection is the angle between the reflected wave and the normal. The
normal is an imaginary line that is perpendicular to the surface at the point of
incidence
 Specular reflection happens when a wave is reflected in a single direction by a
smooth surface
 Diffuse reflection is when a wave is reflected by a rough surface and the reflected rays
are scattered in lots of different directions