devarshi-dt-logo

Question:

In a Young's double slit experiment, the path difference, at a certain point on the screen, between two interfering waves is 1/8th of the wavelength. The ratio of the intensity at this point to that at the centre of a bright fringe is close to:

0.94

0.74

0.85

0.80

Solution:

Δx = λ/8
Δφ = (2π/λ)λ/8 = π/4
I = I₀cos²(π/4)
I/I₀ = cos²(π/4) = (1/√2)² = 1/2 = 0.5
The closest option is 0.74