Question

A trihedral prism with refracting angle 60° provides the least deflection angle 37° in air. Find the least deflection angle of that prism in water.

Answer 1

The least deflection angle is given by the formula,

 is the angle of incidence at first surface and θ is the prism angle. Also from Snell’s law,  n₁ sin α = n₂ sin(θ/2), as the angle of refraction at first surface is equal to half the angle of prism for least deflection

Substituting in the above (1), we get, δ = 8.65°