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JEE Mains · Physics · STD 12 - Wave optics
  • JEE Mains 2020
  • Medium
  • Numerical

In a Young's double slit experiment, \(16\) fringes are observed in a certain segment of the screen when light of wavelength \(700 \,nm\) is used. If the wavelength of light is changed to \(400 \,nm\), the number of fringes observed in the same segment of the screen would be........

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Answer & Solution

Correct Answer

(A) \(28\)

Step-by-step Solution

Detailed explanation

Let the length of segment is " \(\ell^{\prime \prime}\)

Let \(N\) is the no. of fringes in " \(\ell^{\prime \prime}\)

and \(w\) is fringe width.

\(\rightarrow\) We can write

\(N w =\ell\)

\(N \left(\frac{\lambda D }{ d }\right)=\ell\)

\(\frac{N_{1} \lambda_{1} D}{d}=\ell\)

\(\frac{ N _{2} \lambda_{2} D }{ d }=\ell\)

\(N _{1} \lambda_{1}= N _{2} \lambda_{2}\)

\(16 \times 700= N _{2} \times 400\)

\(N _{2}=28\)

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