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Question: Answered & Verified by Expert
In a Young's double slit set-up, light from a laser source falls on a pair of very narrow slits separated by $1.0$ micrometer and bright fringes separated by $1.0$ millimeter are observed on a distant screen. If the frequency of the laser light is doubled, what will be the separation of the bright fringes ?
PhysicsWave OpticsKVPYKVPY 2011 (SB/SX)
Options:
  • A $0.25 \mathrm{~mm}$
  • B $0.5 \mathrm{~mm}$
  • C $1.0 \mathrm{~mm}$
  • D $2.0 \mathrm{~mm}$
Solution:
2378 Upvotes Verified Answer
The correct answer is: $0.5 \mathrm{~mm}$
Separation
$\begin{array}{l}
\text { Bright fringe }=\frac{\lambda D}{d} \\
f \lambda=c
\end{array}$
If $\mathrm{f}$ is doubled
$\lambda$ become halved
$\therefore \beta$ become half
$\beta=\frac{1}{2}=0.5 \mathrm{~mm}$

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