refraction of waves

• Refraction


  Waves can change direction when they change speed moving from one medium to another
• Ray diagram showing refraction

  1. Light ray enters glass block

  2. Velocity of light decreases, causing direction to change towards normal

  3. Light ray passes through glass block

  4. Velocity of light increases, causing direction to change away from normal
• If waves enter or leave the medium at right angles to the surface (along the normal), they do not change direction
• Wavefront


  An imaginary line that connects all the same points in a set of waves
• Wavefront diagram showing refraction

  1. Wavefronts approach air-glass boundary

  2. Parts of wavefronts entering glass slow down, causing wavefronts to bend towards normal

  3. Wavefronts leaving glass speed up, causing wavefronts to bend away from normal

  4. Wavefronts approaching along normal do not change direction
• Refraction can happen when any wave changes speed as it passes from one medium to another