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Question: Answered & Verified by Expert
In Young's double slit experiment, angular width of fringes is $0.20^{\circ}$ for sodium light of wavelength $5890 Å Å$. If complete system is dipped in water, then angular width of fringes becomes
PhysicsWave OpticsJEE Main
Options:
  • A $0.11^{\circ}$
  • B $0.15^{\circ}$
  • C $0.22^{\circ}$
  • D $0.30^{\circ}$
Solution:
1478 Upvotes Verified Answer
The correct answer is: $0.15^{\circ}$
Angular fringe width $\theta=\frac{\lambda}{d} \Rightarrow \theta \propto \lambda$
$\lambda_w=\frac{\lambda_a}{\mu_w}$
So
$\theta_w=\frac{\theta_{\text {air }}}{\mu_{\mathrm{w}}} \quad=\frac{0.20}{\frac{4}{3}}=0.15^{\circ}$

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