Refraction & Diffraction (Oxford AQA IGCSE Physics): Revision Note

Refraction

• Refraction is a type of transmission

  • The wave enters the new medium and emerges from the other side

• Refraction of a wave occurs when a wave changes velocity upon entering a new medium

Refraction

• If the waves slow down

  • The wavefronts will cover less distance in the same amount of time

  • So the wavefronts bunch together and the wavelength decreases

  • The wavefronts will turn towards the normal

• If the waves speed up

  • The wavefronts will cover more distance in the same amount of time

  • So the wavefronts spread out and the wavelength increases

  • The wavefronts will turn away from the normal

• Water waves travel faster on the surface of deeper water than they do on the surface of shallower water

• When the depth of the water changes, refraction can be observed

Refraction of water waves

Diffraction

• Diffraction occurs when a wave meets a gap or an obstacle and the wave spreads out

Diffraction of a wave

• Diffraction is greatest when the wavelength is the same size as the gap

• As the gap gets bigger, the amount of diffraction decreases

Diffraction and gap size

• Diffraction can also occur when waves pass an edge

 Diffraction around an edge