Light and sound

• Light waves are transverse waves that can be reflected or refracted
• The law of reflection is that the angle of incidence is equal to the angle of reflection
• Refraction of light:

  • draw a normal perpendicular to the block
  • shine the light ray through the glass block
  • use crosses to mark the path of the ray
  • join up the crosses with a ruler
  • Measure the angle of incidence and refraction
  • repeat with different angles of incidence and different shaped prisms
• Refractive index = sini/sinr
• To find the refractive index of glass:

  • shine the light ray at an angle to the normal into the glass block
  • Use crosses to mark the path of the ray and then use a ruler to join them up
  • measure angles of incidence and refraction
  • calculate refractive index and find an average from all results
• Total internal reflection is used to transmit signals along optic fibres
• The critical angle is the angle of incidence that produces an angle of refraction of 90°
• When the angle of incidence is greater than the critical angle , total internal reflection occurs
• Critical angle only occurs at a boundary from a high refractive index material to a low refractive index material
• N= 1/sinc
• Sound waves are longitudinal waves that can be reflected or refracted
• 1.       Set up your apparatus as shown in the diagram using a rectangular block.

  2.       Shine the light ray through the glass block

  3.       Use crosses to mark the path of the ray.

  4.       Join up crosses with a ruler

  5.       Draw on a normal where the ray enters the glass block

  6.       Measure the angle of incidence and the angle of refraction and add these to your results table

  7.       Comment on how the speed of the light has changed as the light moves between the mediums.

  8.       Repeat this for different angles of incidence and different glass prisms.