A monochromatic green light of wavelength $520,\text{nm}$ passes through a triangular prism with apex angle $30^{\circ }$. The refractive index of the prism for this light is $1.52$. Assuming small angles, calculate the deviation (in degrees) of the emergent ray from the incident ray.

Step-by-step solution

1. Use the small-angle approximation for a prism: $\delta \approx (n-1)A$ where $n$ is the refractive index and $A$ the apex angle.
2. Substitute $n=1.52$ and $A=30^{circ}$: $\delta =(1.52-1)(30^{circ})=0.52\times 30^{circ}=15.6^{circ}$.
3. State the deviation as $15.6^{circ}$.

Concept tested: Prism deviation formula

Published 1 October 2026 · How this solution was prepared and checked