NTA Abhyas JEE Main2020PhysicsRay OpticsPractice
A light ray is incident on the lower medium boundary at an angle 30 ° with the normal. Which of the following statements is true?
Options
- AIf μ 2 > 2 ,then total deviation is 60 °
- BIf μ 2 < 2 , then total deviation is 30 °
- CIf μ 2 > 2 ,then total deviation is 120 °
- DIf μ 2 < 2 ,then total deviation is 180 °
Correct answer
A. If μ 2 > 2 ,then total deviation is 60 °
Step-by-step solution
For T.I.R. at A 4 sin 3 0 ∘ = μ 2 sin 9 0 ∘ μ 2 = 2 Case -I If μ 2 < 2 , then always T.I.R. takes place and in this situation angle of deviation is 120 o . Case-II μ 2 > 2 , then for the given angle of incidence no. T.I.R takes place at A, so light strikes on interface B for T.I.R. μ 2 sin α = 2 sin 9 0 ∘ or μ 2 = 2 sin α sin α < 1 μ 2 > 2