2019 Wave OpticsYoung's Double Slit Experiment Medium Question 5 of 8 in Young's Double Slit Experiment

In a double slit experiment, when light of wavelength 400 nm was used, the angular width of the first minima formed on a screen placed 1 m away, was found to be $0.2^\circ$. What will be the angular width of the first minima, if the entire experimental apparatus is immersed in water ($\mu_{water}=4/3$)?

A $0.266^\circ$
B $0.15^\circ$
C $0.05^\circ$
D $0.1^\circ$

The answer is B.

Solution

In air, angular fringe width $\theta_0=\frac{\lambda}{d}$. In water, the wavelength becomes $\frac{\lambda}{\mu}$, so $\theta_w=\frac{\theta_0}{\mu}$ $\theta_w=\frac{0.2^\circ}{4/3}=0.15^\circ$

Concept angular fringe width in a medium

Young's Double Slit Experiment in past papers

8 questions from this chapter have appeared across 8 exam years.