A source S is kept directly behind the slit `S_(1)` in a double slit apparatus. What will be the phase difference at P, if a liquid of refraction index `mu`is filled : (wavelength of light in aire is `lambda` due to the source, assume `lgtgtd,Dgtgtd`).

(a) Between the screen and the slits.
(b) Between the slits & the source S. In this case, find the minimum distance between the points on the screen where the intensity is half the maximum intensity on the screen.

Answer

`[(a)Deltaphi=((1)/(l)+(mu)/(D))(pid^(2))/(lambda);(b) Deltaphi=((mu)/(l)+(1)/(D))(pid^(2))/(lambda);D_("min")=(beta)/(4)=(lambdaD)/(4d)]`