Physics for IGCSE & O level - Rays And Waves (Section 4 - No. 32)
What is the critical angle?
The angle of reflection.
The angle of incidence at which refraction is 90 degrees.
The angle of refraction.
The angle between the incident and refracted ray.
Explication
The critical angle is the angle of incidence which leads to a 90-degree angle of refraction.