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Question: Answered & Verified by Expert
In an interference experiment, third bright fringe is obtained at a point on the screen with a light of $700 \mathrm{~nm}$. What should be the wavelength of the light source in order to obtain 5 th bright fringe at the same point?
PhysicsWave OpticsMHT CETMHT CET 2009
Options:
  • A $500 \mathrm{~nm}$
  • B $630 \mathrm{~nm}$
  • C $750 \mathrm{~nm}$
  • D $420 \mathrm{~nm}$
Solution:
2602 Upvotes Verified Answer
The correct answer is: $420 \mathrm{~nm}$
$n_{1} \lambda_{1}=n_{2} \lambda_{2}$
$$
\Rightarrow \quad 3 \times 700=5 \times \lambda_{2}
$$
$$
\Rightarrow \quad \lambda_{2}=420 \mathrm{~nm}
$$

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