Question

In Young's double-slit experiment, an interference pattern is obtained on a screen by a light of wavelength 4000 Å, coming from the coherent sources S₁ and S₂ At certain point P on the screen, third dark fringe is formed. Then the path difference S₁P - S₂P in microns is ______.

Options

• 0.75

• 1

• 3.0

• 4.5

Answer 1

In Young's double-slit experiment, an interference pattern is obtained on a screen by a light of wavelength 4000 Å, coming from the coherent sources S₁ and S₂ At certain point P on the screen, third dark fringe is formed. Then the path difference S₁P - S₂P in microns is 1.

Explanation:

For dark fringe at P,

S₁P - S₂P = `Deltal (2"n" - l) lambda/2`

Here, n = 3 and `lambda` = 4000

`therefore Deltal = (5lambda) /2 = 5 xx 4000/2` =  10000 Å =1 micron