In a Young's double slit experiment, an angular width of the fringe is 0 . 35 ° on a screen placed at 2 m away for particular wavelength of 450 nm . The angular width of the fringe, when whole system is immersed in a medium of refractive index 7 5 , is 1 α . The value of α is _____ .

Step-by-step solution

Angular fringe width is given by θ = λ D , where, D is the distance between the source and the screen and λ is the wavelength of the light. We have, θ 1 θ 2 = λ 1 λ 2 Then, θ 2 = 0.35 ∘ 450   nm × 450   nm 7 5 = 0.25 ∘ = 1 4 ∵ λ 2 = λ 1 μ Thus, value of α = 4 .