Question

an equilateral prism has an angle of minimum deviation 30 find total deviation if the ray is incident normally to the surface​

Answer 1

Explanation:

As per the given criteria,

angle of deviation, δ=30

∘refractive index of the prism, μ= 2

As the prism is equilateral, the refractive angle, A=60

∘

And we know,

μ= sin 2Asin( 2A+δ m )Substituting the values, we get2 = sin 260sin( 260+δ m )⟹ 2= sin30sin( 260+δ) m⟹ 2 × 21 =sin( 260+δ m )⟹ 260+δ m =sin −1 ( 2 1 )⟹ 260+δ m =45⟹δ m=90−60=30 ∘

Hence the minimum deviation angle is equal to the deviation angle, hence at minimum deviation condition the ray travels parallel to the base inside the prism.

The angle between the ray and base inside the prism is zero.