26. In the screen with a circular hole of radius r = 1,5 mm is normally incident parallel beam of monochromatic light of wavelength λ = 0,5 mm. The observation point is on the axis of the hole at a distance b = 1,5 m from it. Determine: 1) the number of Fresnel zones fit into the hole; 2) dark or bright ring seen in the center of the diffraction pattern when placed at the point of the screen.

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