# Concept of Prism

**Question**

Consider a thin prism.

Find the deviation (in degrees)

(a) !!178!!

(b) !!2!!

(c) !!179!!

(d) !!1!!

**Solution**

We will use the formula of deviation for thin prism.

!!delta = A(mu-1)!!, where !!A!! is prism angle and !!mu!! is refractive index of the prism.

!!delta = 2^0 (1.5-1)= 1^0 !!

Then it will reflect by mirror, so final deviation will be

!!=> 180^0 -1 = 179^0!!

Therefore option (c) is correct.