Question

A prism produces a minimum deviation $\delta$ in a light beam. If three such prisms are combined, the minimum deviation produced will be :

• A. 4 $\delta$
• B. 2 $\delta$
• C. $\delta$
• D. $0$

Answer 1

The correct option is C $\delta$

The minimum deviation depends only on the axial angle of a prism. If all the 3 combined prisms are identical, the deviation produced will be the same as for 1 prism.

Here deviation from each prism is $\delta$

So, ${\delta }_{net}=\delta -\delta +\delta$

$=\delta$

( because middle prism is reversed so its deviation is negative )

So, minimum deviation from 3 prisms is $\delta$