Q. In a Young’s double slit experiment, the fringe width is found to be 2 mm, when light of wavelength 6000 $\mathring{\mathrm{A}}$ is used. Find the change in fringe width if the whole apparatus is immersed in water of refractive index 1.33.
A) 0.5 mm
B) 1 mm
C) 1.5 mm
D) 2 mm
Explanation
(c) Fringe width $\beta = 2\ mm = 2 \times 10^{- 3}\ m$
$\ \ \lambda = 6000\ \mathring{\mathrm{A}}$
$\mu = 1.33$
$\beta^{'} = \ ?$
$\beta^{'} = \frac{\beta}{\mu} = \frac{2}{1.33} = 1.5\ mm$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.