±«Óătv

Critical angle and total internal reflection - Higher - CCEATotally reflecting prisms

Ray diagrams explain reflection in a plane mirror. Beyond a critical angle all waves are totally internally reflected. Optical fibres use total internal reflection to carry light and information.

Part of Physics (Single Science)Light

Totally reflecting prisms

Total internal reflection inside a 45 degrees glass prism; the critical angle for the type of glass used to make the prism = 45 degrees; the ray of light is turned through 90 degrees.
  • Total internal reflection inside a 45o glass prism.
  • The critical angle for the type of glass used to make the prism = 42o.
  • The ray of light is turned through 90o.
  • At A the ray of light is incident along the normal and passes straight through into the glass prism without being bent.
  • At B the angle of incidence at the glass – air boundary is 45o which is greater than the . Total internal reflection occurs, and the is 45o.
  • At C the ray of light is incident again along the normal and passes straight through into air without being bent.
Light ray being turned through 180 degrees inside a 90 degree prism
  • Total internal reflection inside a 90o glass prism.
  • The critical angle for the type of glass used to make the prism = 42o.
  • The ray of light is turned through 180o.
Next page
Bicycle and car reflector
Previous page
Critical angle investigation

More guides on this topic

Related links