All Problems

Diffraction of Light

Problem 5.109

A point source of monochromatic light is positioned in front of a zone plate at a distance a=1.5 ma=1.5 \mathrm{~m} from it. The image of the source is formed at a distance b=1.0 mb=1.0 \mathrm{~m} from the plate. Find the focal length of the zone plate.

Reveal Answer
f=ab/(a+b)=0.6 m. This value corresponds to the principal focal point, apart from which there are other points as well.f=a b /(a+b)=0.6 \mathrm{~m} . \text { This value corresponds to the principal focal point, apart from which there are other points as well.}
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