Question

In Young's double-slit experiment, the slits are illuminated by monochromatic light. The entire set-up is immersed in pure water. Which of the following act cannot restore the original fringe width?

• A. Bringing the slits close together
• B. Moving the screen away from the slit plane.
• C. Replacing the incident light by that of longer wavelength
• D. Introducing a thin transparent slab in front on one of the slits

Answer 1

The correct option is D Introducing a thin transparent slab in front on one of the slits

When we introduce a thin transparent slab in front of one of the slits only the path difference is changed and it does not restore the original fringe width.
Option $D$ is correct