Question

If Young's double slit experiment is performed in water,

• A. the fringe width will decrease
• B. the fringe width will increase
• C. the fringe width will remain unchanged
• D. there will be no fringe

Answer 1

The correct option is A the fringe width will decrease

Fringe width $\beta =\frac{\lambda D}{d}$

If $\mu (>1)$ is refractive index of water, then wavelength reduces by $\mu$ factor

New fringe width ${\beta }^{\prime }=\frac{\lambda D}{\mu d}$

Therefore in water, fringe width decreases.