Question

Find the right condition(s) for Fraunhoffer diffraction due to a single slit.

• A. Source is at infinite distance and the incident beam has converged at the slit.
• B. Source is near to the slit and the incident beam is parallel.
• C. Source is at infinity and the incident beam is parallel.
• D. Source is near to the slit and the incident beam has converged at the slit.

Answer 1

Answer: (B), (C)

For Fraunhofer diffraction, incident beam should be parallel.
This can be achieved when
(a) Source is placed at focus of converging lens.
(b) Source is at infinite distance.