Edexcel IGCSE Physics 3.20 Total internal reflection
Practise explaining total internal reflection in optical fibres, prisms and glass-air boundaries using critical angle and refractive index.
- Syllabus
- First assessment 2019
- Course
- Physics 4PH1
Practise explaining total internal reflection in optical fibres, prisms and glass-air boundaries using critical angle and refractive index.
This question is about refraction.
The torch is moved below the surface of the water. Light from the torch is incident on the water surface at an angle greater than the critical angle.
A ray of light leaves the torch as shown in the diagram.
Complete the path of the ray of light.

single straight ray reflected downwards
from water surface;
angle correct by eye;
any ray above water surface
scores zero