Ray & Wave Optics
“In Young’s double slit experiment, how does fringe width change when the apparatus is immersed in a liquid of refractive index μ?”
Solution by Dr. Ananya Rao:Answered in 42 mins
Fringe width is given by β = λD/d. When the apparatus is immersed in liquid of refractive index μ, the wavelength decreases according to λ’ = λ/μ. Therefore, the new fringe width becomes β’ = β/μ. This causes the interference fringes to become narrower and closer together.