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Problem 2: Monochromatic light of wavelength 589.2 nm is used to illuminate the narrow slits 1 mm apart. Find the position of the first dark and first bright fringes on a screen 100 cm away.

Solution

Given

Wavelength of the incident light = 589.2 nm

Slits separation = 1 mm = 10-3 m

Distance between slits and screen = L = 100 cm = 1 m

Required

Position of the first dark fringe = Ydark 1 =?

Position of the first bright fringe = Ybright 1 =?

Formula

For dark fringe, 

For bright fringe,

 

Now to find the first dark fringe, put m = 0 in formula (1).

Similarly, to find first bright fringe, put m = 1 in formula (2).

 

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  1. Pingback:Numerical Problems, Physical Optics, … msa – msa

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