Question

A monochromatic beam of light is used for the formation of fringes on the screen by illuminating the two slits in the Youngs double-slit interference experiment. When a thin film of mica is interposed in the path of the interference beams, then

• A. The fringe width increases
• B. The fringe width decreases
• C. The fringe width remains the same but the pattern shifts
• D. The fringe pattern disappears

Answer 1

Answer: (C)

The fringe width remains the same but the pattern shifts

Fringe width $=\frac{D\lambda }{d}$, No depend on slab But the pattern will shift by certain amount since $(\mu -1)$ will get added in path difference