Refraction of waves

• Constructing ray diagrams to show refraction of a wave

  1. Draw a ray of light entering a glass block

  2. Light velocity decreases when passing from air into glass, causing the light waves to bend towards the normal

  3. Light velocity increases when passing from glass back to air, causing the light waves to bend away from the normal

  4. Light does not change direction if it enters/leaves the medium at right angles to the surface (along the normal)
• Wavefront

  An imaginary line that connects all the same points in a set of waves
• Using wavefront diagrams to explain refraction

  1. Wavefronts approach the boundary between air and glass

  2. Parts of the wavefronts entering the glass slow down, causing the wavefronts to get closer together and the waves to bend towards the normal

  3. When waves speed up as they leave the glass, the wavefronts bend away from the normal
• Waves can change direction when they change speed moving from one medium to another
• If waves enter or leave the medium at right angles to the surface (along the normal), they do not change direction
• When waves speed up, they change direction away from the normal
• When waves slow down, they change direction towards the normal