JEE Advanced2017PhysicsRay OpticsActual
For an isosceles prism of angle A and refractive index μ it is found that, the angle of minimum deviation is δ m = A . Which of the following options is/are correct?
Options
- AFor this prism, the emergent ray at the second surface will be tangential to the surface when the angle of inc
- BFor the angle of incidence i 1 = A , the ray inside the prism is parallel to the base of the prism.
- CAt minimum deviation, the incident angle   i 1 and the refracting angle r 1 at the first refracting surfa
- DFor this prism, the refractive index μ and the angle of prism A are related as A = 1 2 cos - 1 μ 2
Correct answer
A. For this prism, the emergent ray at the second surface will be tangential to the surface when the angle of inc
Step-by-step solution
i = e (for minimum deviation) r 1 + r 2 = A , r 1 = r 2 i δ m = 2 i - A = A (given) ⇒ i = A ⇒ r 1 = A 2 = i 2 i i μ = sin A sin A 2 = 2 cos A 2 ⇒ A = 2 cos - 1 μ 2 i i i μ sin r 2 = 1 sin r 2 = 1 μ r 1 + r 2 = A r 1 = A - r 2 = A - sin - 1 1 μ sin i = μ sin r 1 i = sin - 1 μ sin A - sin - 1 1 μ i 1 = sin - 1 μ 2 - 1 sin A - cos A = sin - 1 μ sin A - θ C H e r e , μ = 2 cos A 2 i v Condition of min. deviation i = e a n d r 1 = r 2 = A 2