(PP6) angles of incidence

• use ray tracing to measure the angles of incidence and refraction when light is refracted by a glass block
• the angles of incidence and refraction are measured from a line at right angles to the glass surface known as the normal
• Independent variable is the angle of incidence.
• Dependent variable is the angle of refraction
• Control variables are the material of the block, the shape of the block and the colour of the light.
• Light is travelling from air to glass and so is refracted towards the normal.

  As the angle of incidence increases the refracted light will bend from a bigger initial angle, and so the angle of refraction will also be bigger.
• The main cause of error is the measurement of the angles of incidence and refraction.

  This can be kept to a minimum by:

  • replacing the block carefully on its outline
  • ensuring that the power pack is set to 12 V, so that the ray box is at maximum brightness;
  • doing the experiment in a dark room so that the emergent ray can be easily seen and marked.
• the angle of incidence is not directly proportional to the angle of refraction as the line of best fit is not a straight line through the origin