In an opaque screen with a hole diameter of 1.8 mm is normally incident plane light wave length of 0.5 microns. The observation point is located on the center line and removed from the screen at a distance of 0.4 m. To determine the number of Fresnel zones, which are stacked in the bore, and the result of the diffraction of light on the axis. What changes will take place, if l is increased to 0.8 m?

Detailed solution with a short recording conditions, laws and formulas used in the decision, the withdrawal of the calculation formula and the answer.
If you have any questions about the decision to write. I try to help.