# Question #e5a96

Mar 25, 2016

#### Explanation:

Please refer to the figure above.

$A B C$ is a cross-section of a triangular block of transparent material. Usually it is in the form of an isosceles triangle. Triangular block is called Prism.

A ray of light $P Q$ is incident on one of its faces at point $E$, making an $\angle P E N$, also called the angle of incidence $\angle i$, at the point of incidence. $N N '$ being the normal at the point of incidence.

As the ray of light enters the transparent material, it moves from air, a rarer medium, to a denser medium. Refractive index $\mu$ of the material of the block being more than that of air. The ray of light is refracted and bends towards the normal.

The ray of light moves in a straight path through the block and impinges the other face of the block at $F$. As it emerges out of the block, it moves from a denser to a rarer medium, and therefore, bends away from the normal $M M '$ at point $F$. Once out of the block it proceeds again along a straight line path $R S$ as the emergent ray.

In the ray diagram angle of emergence and the angle of deviation are also depicted.