Ina double slit experiment the angular width of a fringe is found to be `0.2^(@)` on a screen placed 1m away.The wavelength of light is 600 nm. What will be the angular width of the fringe if the entire experimental apparatus is immersed in water? Take refractive index of water of be`4/3`

Explanation

Angular size `theta= (lamda)/d` is independent of D.
`:. (theta.)/(theta)=(lamda.)/(lamda)` but `lamda. =(lamda)/n` where n is the refractive index
`:. Theta.=(theta)/(lamda.)xx(lamda.)/n=(theta)/n=(0.2^(@))/((4//3))=0.15^(@)`