Question

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 _________.

Answer 1

Correct Answer: 4

The correct answer is 4
Angular fringe width
\(θ=\frac{λ}{D}\)
So
\(\frac{θ_1}{λ_1}=\frac{θ_2}{λ_2}\)
\(θ_2=\frac{0.35^∘}{450 nm}×\frac{450 nm}{715}\)
\(=0.25^∘=\frac{1}{4}\)
\(\therefore\) value of α = 4