BITSAT2018PhysicsWave OpticsActual
In Young's double slit experiment, intensity at a point is 1 4 of the maximum intensity. Angular position of this point is
Options
- Asin - 1 λ d
- Bsin - 1 λ 2 d
- Csin - 1 λ 3 d
- Dsin - 1 λ 4 d
Correct answer
C. sin - 1 λ 3 d
Step-by-step solution
I = I max cos 2 ϕ 2 I max 4 = I max cos 2 ϕ 2 cos ϕ 2 = 1 2 ϕ 2 = π 3 ⇒   ϕ = 2 π 3 = 2 π λ × Δ x . . . . i where, Δ x = d sin θ Putting the value of Δ x in Eq. (i), we get sin θ = λ 3 d θ = sin - 1 λ 3 d