Question

When white light passes through a thin glass prism, one gets spectrum on the other side of the prism. In the emergent beam, the ray which is deviating least is :

• A. Violet ray
• B. Green ray
• C. Red ray
• D. Yellow ray

Answer 1

The correct option is C Red ray

We know that for the thin prism,
Angle of deviation $\left(\delta \right)$ :
$\delta \propto (\mu -1)$

So, as the value of refractive index increases angle of deviation also increases.

We know that for the given colours of light referactive index is maximum for Violet light and minimum for Red light.

Therefore, angle of deviation will be maximum for the Violet light and minimum for the Red light.

Hence, option $\left(c\right)$ is the correct answer.