NTA Abhyas JEE Main2020PhysicsWave OpticsPractice
In the adjacent diagram, CP represents wavefront and AO and BP corresponding two rays. One particular condition on θ for destructive interference at P between the ray BP and reflected ray OP is cosθ = λ nd , where n is
Correct answer
2
Step-by-step solution
Path difference = CO + OP + λ 2 = OPcos 2 θ + OP + λ 2 = OP ( 1 + cos 2 θ ) + λ 2 OPcosθ   =   d Path difference = d cosθ ( 1 + cos 2 θ ) + λ 2 = d cosθ ⋅ 2 cos 2 θ + λ 2 = 2 dcosθ + λ 2 ⇒ 2 dcosθ = kλ    ( k ∈ N ) For k = 1 , 2 dcosθ = λ cosθ = λ 2 d