Problem 5.117

A plane monochromatic light wave falls normally on an opaque screen with a long slit whose shape is shown in Fig. 5.25 . Making use of Fig. $5.19,$ find the ratio of intensities of light at points $1,2,$ and 3 located behind the screen at equal distances from it. For point 3 the rounded-off edge of the slit coincides with the boundary line of the first Fresnel zone.