1. Relation between angle of incidence and deviation in a prism

For a prism, the angle of deviation is

where:

• $i$ = angle of incidence,
• $e$ = angle of emergence,
• $A$ = angle of prism.

As $i$ changes, $e$ also changes, so $\delta$ varies with $i$.

2. Nature of the graph

For a prism, the deviation first decreases with increase in angle of incidence, reaches a minimum value $\delta_{\min}$, and then increases again.

So the graph of $\delta$ versus $i$ is a U-shaped curve.

3. Condition at minimum deviation

At minimum deviation,

and the path of the ray through the prism is symmetric.

Thus the $\delta$-$i$ graph has a turning point at $\delta_{\min}$.

4. Identify the correct option

Hence the correct graphical representation must show:

• deviation decreasing initially,
• attaining a minimum,
• then increasing.

That corresponds to Option B.

5. Comparison with stored answer

Stored correct answer: B

Derived answer: B

So the derived answer agrees with the stored answer.