Question

In Young’s double slit experiment, the angular width of a fringe is \(0.2^\circ\). If the entire apparatus is immersed in water of refractive index \(4/3\), the angular width of the fringe will be

• A. \(0.18^\circ\)
• B. \(0.15^\circ\)
• C. \(0.06^\circ\)
• D. \(0.12^\circ\)

Hint:

Fringe width decreases when experiment is performed in a denser medium.

Answer 1

The Correct Option is B

Step 1: Angular fringe width relation.
\[ \theta = \frac{\lambda}{d} \]
Step 2: Effect of medium.
Wavelength in medium:
\[ \lambda' = \frac{\lambda}{\mu} \]
Step 3: New angular width.
\[ \theta' = \frac{\theta}{\mu} = \frac{0.2^\circ}{4/3} \]
Step 4: Calculation.
\[ \theta' = 0.2 \times \frac{3}{4} = 0.15^\circ \]
Step 5: Conclusion.
The angular width of the fringe becomes \(0.15^\circ\).