Q2DQ - University Physics with Modern Physics

Question

What is the difference between Fresnel and Fraunhofer diffraction? Are they different physical processes? Explain.

Step-by-Step Solution

Answer

In Fresnel diffraction, the slit and the screen are a finite distance apart, while in Fraunhofer diffraction, the slit and the screen are infinitely apart. In both the cases, the process that is taking place is the same.

Step 1: Fraunhofer and Fresnel Diffraction

When the source and the observer are so far away from the obstructing surface that the outgoing rays can be considered parallel, it is called Fraunhofer diffraction. When the source or the observer is relatively close to the obstructing surface, it is Fresnel diffraction.

Step 2: Compare Fresnel diffraction and Fraunhofer experiment

In Fresnel diffraction, the source of light and the screen are effectively at finite distances from the obstacle. 

In Fraunhofer diffraction, the source of light and the screen are effectively at infinite distances from the obstacle. 

In both the cases, the process taking place is the same. Whether Fresnel or Fraunhofer, both are two cases of a single process, called diffraction.