Question

In Young's double slit experiment, fringe width decreases by 25% when apparatus is immersed in a liquid. Refractive index of the liquid is

• A. 1.5
• B. 1.33
• C. 1.43
• D. 1.62

Answer 1

Answer: (B)

1.33

Answer 2

When apparatus is immersed in liquid of refractive index $\mu$, fringe width,
$\beta ' = \frac{\beta}{\mu}$
Now $\beta' = \frac{75}{100} \beta$
$\therefore \, \, \frac{75}{100} \beta = \frac{\beta }{\mu} or \mu = \frac{100}{75} = \frac{4}{3} = 1.33$