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Using monochromatic light of wavelength \lambda , an experimentalist sets up the Young’s double slit experiment in three ways as   shown.

If she observes that  y= \beta ', the wavelength of light used is :      



  • Option 1)

    520 nm

  • Option 2)

    540 nm

  • Option 3)

    560 nm

  • Option 4)

    580 nm


Answers (1)


As we learnt in

Displacement of fringe -

\Delta y= \frac{D}{d}\left ( \mu -1 \right )t

Shift in position of fringes


- wherein

If sheet is placed in front of one of slit.


 t=1.8\times 10^{-6}m


n = 2

Now (\mu-1)t=n\lambda\ \;\Rightarrow\ (1.6-1)\times 1.8\times 10^{-6}=2\lambda

\lambda=\frac{1.8\times10^{-6}\times0.6}{2}=540\ nm

Correct option is 2.


Option 1)

520 nm

This is an incorrect option.

Option 2)

540 nm

This is the correct option.

Option 3)

560 nm

This is an incorrect option.

Option 4)

580 nm

This is an incorrect option.

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