The angle of incidence when the angle of refraction is 90 o, and the ray changes from just refracting to total internal reflection, is called the critical angle. The diagram below shows the light ...

They are shaped in a way that refracts light so it focuses at a point. Just like ray diagrams showing reflection, all angles are measured from the normal – a line at 90° to the refracting surface.

The other mirror (mirror B in the diagram) is attached to a movable arm. Light from an object ... can be moved to a position where the sun's reflection off the mirror also reflects off mirror ...