69. The diffraction pattern is observed at a distance of 1 m from the point source of monochromatic light (λ = 0,5 mm). Midway between the light source and the screen is a circular aperture diaphragm. Determine the radius of the hole, where the center of the diffraction pattern on the screen will be the most dark.

Detailed solution. Decorated in Microsoft Word 2003. (Target decided to use formula editor)