Question

Two beams of red and violet colours are made to pass separately through prism (angle of the prism is ${60}^o$). In the position of minimum deviation, the angle of refraction will be:

• A. ${30}^o$ for both the colours
• B. greater for the violet colour
• C. greater for the red colour
• D. equal but not ${30}^o$ for both the colours

Answer 1

The correct option is A ${30}^o$ for both the colours

In the case of minimum deviation $-$ $i=e$ and

$\Rightarrow r_1=r_2=\frac{A}{2}$

Angle of refraction $=r_1=r_2=\frac{{60}^0}{2}={30}^0$

It is independent of $\mu ,$ so will be same for both colours.

Hence, the answer is ${30}^0$ for both the colours.