Total internal reflection
Total internal reflection is taught in school science labs using a semi-circular glass block. A ray box shines a light ray onto the glass. The semi-circular shape ensures that a ray pointing towards the center of the flat face will hit the surface at right angles.This prevents refraction at the air/glass boundary.
At the glass/air boundary what happens will depend on the angle.
|θ1 <θc||θ2 >θc|
| the ray will split.
Some of the ray will reflect off the boundary,
and some will refract as it passes through.
|All of the ray reflects from the boundary.|
None passes through.
The colour of the rays in the diagram is there to easily distinguish the rays, it is not meant to indicate any colour dependence.