Question

Calculate critical angle for right angle prism with apex angle 30o and refraction index 1.5. Consider that light is incident on flat surface of prism. Calculate minimum deviation angle of prism.

Answer 1

Solution:

For small angle prism

δ

1

=(μ−1)A

⟹δ

1

=(1.5−1)(4)

⟹δ

1

=2

∘

So ray is incident on plane mirror at 2

∘

,

Hence δ

2

=S

mirror

=180

∘

−2(2

∘

)=176

∘

Total reflection = δ

1

+δ

2

=176

∘

+2

∘

=178

∘

clockwise.