Describe what happens to the Fraunhofer single slit diffraction pattern if the whole apparatus is immersed in water
(ii) Light of wavelength 6500 A nm is incident on a narrow slit. The angle between the first minima on one side of the central maxima and the first minima on the other side is `60^(@)`. Find the width of the slit.

Answer

Width of central maximum `(2Dlambda)/(a)`. On immersing in water the wavelength of light decreases and hence width of central maximum decreases
(ii) For first minima `d sintheta =30^(@),`lambda=6500xx10^(-10)``therefore`   Here `1.3xx10^(-6)`