Paper 3 · Waves and Interference
What is meant by the critical angle, for light travelling from a denser medium towards a less dense one?
Model answer
gives 90 degree refraction
Also accepted: the angle of incidence that gives a refracted angle of 90 degrees, incident angle giving a 90 degree refracted angle, the incidence angle for which the refracted ray grazes the boundary at 90 degrees
Explanation: The critical angle is the angle of incidence, for light travelling from a denser to a less dense medium, which gives a refracted angle of 90 degrees.
Derived from ZIMSEC Physics Paper 3, June 2003, Q6