Question

If Young’s double slit experiment is performed in water instead of air, then 

(a) no fringes would be seen 

(b) fringe width would decrease 

(c) fringe width would increase 

(d) fringe width would remain unchanged

Answer 1

Answer is (b) fringe width would decrease

Fringe width, β = \(\frac{D\lambda}{d}\)

or β ∞ λ

If the experiment is performed in water,

wavelength λ decreases, so fringe width also decreases.