Everything CCEA students need to know about critical angle and total internal reflection. ... The diagram below shows the path of a ray of red light passing through a glass prism.

Teacher Notes. Your class could repeat the demonstration with the glass and the coin. Ask them to draw light ray diagrams to show what happens when they move their head higher or lower.

When a ray of light that is travelling through a piece of glass strikes the interface between the glass and the air, it changes direction according to Snell’s law. If the angle of incidence is less ...