Question

Drive expression for focal length of zone plate

Answer 1

Explanation:

according to the question answer is to add ABC

Answer 2

rn = root n lambda f. A zone plate is a device used to focus light or other things exhibiting wave character. Unlike lenses or curved mirrors however, zone plates use diffraction instead of refraction or reflection. Based on analysis by Augustin-Jean Fresnel, they are sometimes called Fresnel zone platesin his honor.