Wave Interactions (Edexcel GCSE Physics)

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Wave Interactions

  • When a wave reaches an interface (or boundary) between two materials - for example, air and water - the wave may be:
    • Reflected
    • Refracted
    • Transmitted
    • Absorbed

Reflection

  • Reflection occurs when:

A wave hits a boundary between two media and does not pass through, but instead stays in the original medium

  • Some of the wave may also be absorbed or transmitted
    • Echos are examples of sound waves being reflected off a surface

  • Flat surfaces are the most reflective
    • The smoother the surface, the stronger the reflected wave is

  • Rough surfaces are the least reflective
    • This is because the light scatters in all directions

  • Opaque surfaces will reflect light which is not absorbed by the material
    • The electrons will absorb the light energy, then reemit it as a reflected wave

Refraction

  • Refraction occurs when:

A wave changes speed at the boundary between two materials of different densities

  • Glass and water are both denser than air, so light waves passing from air into them will slow down (and speed up if going from them into air)
  • The change in speed at the boundary can sometimes causes the wave to change direction
    • Lenses make use of refraction to bend light waves and help focus it in glasses and cameras

  • Sound, water, electromagnetic and seismic waves can all be refracted

Transmission

  • Transmission occurs when:

A wave passes through a substance

  • For light waves, the more transparent the material, the more light will pass through
  • Transmission can involve refraction but is not exactly the same
  • For the process to count as transmission, the wave must pass through the material and emerge from the other side
  • When passing through a material, waves are usually partially absorbed
  • The transmitted wave may have a lower amplitude because of some absorption
    • For example, sound waves are quieter after they pass through a wall

Transmission of wave, downloadable IGCSE & GCSE Physics revision notes

When a wave passes through a boundary it may be absorbed and transmitted

Absorption

  • Absorption occurs when:

Energy is transferred from the wave into the particles of a substance

  • Waves can be partially or completely absorbed
    • Sound waves are absorbed by brick or concrete in houses

  • Light will be absorbed if the frequency of light matches the energy levels of the electrons
    • The light will be absorbed, and then reemitted over time as heat

  • If an object appears red, this means:
    • Only red light has been reflected
    • All the other frequencies of visible light have been absorbed

Absorption, downloadable IGCSE & GCSE Physics revision notes

The object is seen as red since the red light is reflected whilst the other colours are absorbed

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Ashika

Author: Ashika

Expertise: Physics Project Lead

Ashika graduated with a first-class Physics degree from Manchester University and, having worked as a software engineer, focused on Physics education, creating engaging content to help students across all levels. Now an experienced GCSE and A Level Physics and Maths tutor, Ashika helps to grow and improve our Physics resources.