Explain the path of the light traveling in air incident on a rectangular glass block and emerging out into the air from the opposite face. Draw a ray diagram to show the complete path of this ray of light.

A ray of light AO traveling in air is incident on a rectangular glass block at point O. On entering the glass block, it gets refracted and bends towards the normal ON₁. A second change of direction takes place when the ray of light OO¢ traveling in the glass block emerges into air at point O . Since the ray of light OO¢ now goes from a denser medium 'glass' into the rarer medium 'air', it bends away from the normal ON ₂ and takes the direction OB, which is called emergent ray. The incident ray AO and the emergent ray OB are parallel to each other.