Q 12-10-099JEE MainJEE Main 2022 (26 Jul, Shift 1)Easy
In Young's double slit experiment, the fringe width is $12\ \text{mm}$. If the entire arrangement is placed in water of refractive index $\dfrac43$, then the fringe width becomes (in mm)
Answer: (B) 9
$\beta = \dfrac{\lambda D}{d}$ and the wavelength in water is $\dfrac{\lambda}{\mu}$:
$$\beta' = \frac{\beta}{\mu} = \frac{12}{4/3} = 9\ \text{mm}$$
Solution by Sreeraj P, M.Sc Physics