Question

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A ray is incident at an angle of incidence $i$ on one surface of a small angle prism (with angle of prism $A$) and emerges normally from the opposite surface. If the refractive index of the material of the prism is $\mu$, then the angle of incidence is nearly equal to:

• A. $\mu A$
• B. $\frac{\mu A}{2}$
• C. $\frac{A}{2\mu }$
• D. $\frac{2A}{\mu }$

Answer 1

The correct option is A $\mu A$


Angle of incidence = $i$
Angle of prism = $A$
Angle of emergence = $e$
Refractive index of the material = $\mu$

From Snell's law,
$1\times \sin i=\mu \times \sin A$

For small angle approximation, $\sin A\approx A$ and $\sin i\approx i$.

So, $i=\mu A$