A plane light wave with wavelength λ = 0.60μm falls normally on a sufficiently large glass plate having a round recess on the opposite side (Fig. 5.2i). For the observation point P that recess corresponds to the first one and a half Fresnel zones. Find the depth h of the recess at which the intensity of light at the point P is
(a) Maximum;
(b) Minimum;
(c) Equal to the intensity of incident light.

"h iP