a) Two slits each of width .05 mm and separated by 0.5 mm in y-direction are ill

Question

a) Two slits each of width .05 mm and separated by 0.5 mm in y-direction are illuminated by laser light travelling in x-direction. The distance between successive interference fringes on a screen 2.0 m away from the plane of the slits in x-direction is measured to be 2.5 mm along y axis? Calculate the wavelength of the laser light. b) How far from the center of the pattern will the first minimum of the single slit diffraction appear screen? c) What will be the number of interference fringes inside the central diffraction peak?

Explanation / Answer

use for Interferecne pattern

Y = mLR/d

d is slit width = 0.05 mm

R is the distance from slit to screen

L is waveLength = ?

m is order

Y is fringe width

L = Y d/mR

L = (2.5*10^-3 * 0.5*10^-3) /(1 *2)

L = 625 nm

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for m = 0.5

Y = (0.5 * 625 *10^-9 * 2)/(0.5*10^-3)

Y = 1.25 mm

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use d sin theta = mL

for theta = 90 deg

m = 0.05*10^-3* sin 90/(625*10^-9)

m = 80

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