Problem 5.116

A plane monochromatic light wave of intensity $I_{0}$ falls normally on an opaque screen with a long slit having a semicircular cut on one side (Fig. 5.24$) .$ The edge of the cut coincides with the boundary line of the first Fresnel zone for the observation point $P$. The width of the slit measures 0.90 of the radius of the cut. Using Fig. $5.19,$ find the intensity of light at the point $P$.