A point source S emitting light of wavelength 600 nm is placed at a very small height h above a flat figure. The intensity of the reflected light id 36% of the incident intensity. Interference fringe are observed on a screen placed parallel to the reflecting surface at a very large distance D from it.
a. What is the shape of the interference fringe on the screen?
b. Calculate the ratio of the minimum to the maximum intensities in the interference fringes formed near point P (shown in the figure).
c. If the intensity at point P corresponds to a maximum, calculate the mininum distance through which the reflecting surface. AB should at P again becomes maxinum.

Explanation

(a) circular, (b) `1/(18)`, (c ) 300nm