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When diffraction is performed in water then why will the fringes will be smaller in number than when it is performed in air?

When diffraction is performed in water then why will the fringes will be smaller in number than when it is performed in air?

Grade:12

1 Answers

Arun
25757 Points
4 years ago

Maxima for a double slit occur when n lambda = d sin (theta)

so the angles between maxima (and hence the spacing) depends on sin(theta)

Reaaranging: sin (theta) = n lambda/d

When the apparatus is put in water, lambda changes. The velocity in water is less so mthe distance travelled durin on e period is less ie the wavelength (lambda) decreases. So sin(theta) decreases and hence the spacing between the maxima.

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