Question

What is the variation in the pattern observed for single slit Fresnel diffraction than single slit Fraunhofer Diffraction?

(a) The pattern is not hyperbolic

(b) The fringes are too thin

(c) The region of minimum intensity is not completely dark

(d) The fringes are colored

I got this question in exam.

This intriguing question comes from Differences of Fresnel and Fraunhofer Diffraction topic in portion Diffraction of Engineering Physics II

Answer 1

Right answer is (c) The region of minimum intensity is not completely dark

The explanation: The diffraction pattern due to the single slit Fresnel Diffraction is similar to single slit Fraunhofer Diffraction, except the regions of minimum intensity are not completely dark. This is so because there is never a complete destructive interference in Fresnel Diffraction.