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Question: Answered & Verified by Expert
A light wave is incident normally over a slit of width $24 \times 10^{-5} \mathrm{~cm}$. The angular position of second dark fringe from the central maxima is $30^{\circ}$. What is the wavelength of light
PhysicsWave OpticsJEE Main
Options:
  • A $6000 Å$
  • B $5000 Å$
  • C $3000 Å$
  • D $1500 Å$
Solution:
2241 Upvotes Verified Answer
The correct answer is: $6000 Å$
For second dark fringe $d \sin \theta=2 \lambda$
$\begin{aligned} & \Rightarrow \quad 24 \times 10^{-5} \times 10^{-2} \times \sin 30=2 \lambda \\ & \Rightarrow \quad \lambda=6 \times 10^{-7} \mathrm{~m}=6000 Å\end{aligned}$

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