Question

If Young's double slit experiment is performed in water instead of air, then

• A. No fringes would be seen
• B. Fringe width would decrease
• C. Fringe width would increase
• D. Fringe width would remain unchanged

Answer 1

The correct option is B Fringe width would decrease

In water, speed of light decreases.

Since frequency remains same, therefore the wavelength must decrease.

The formula for fringe width is $\frac{\lambda D}{d}$.

Thus, fringe width decreases in water because wavelength of light decreases.