IN A YOUNG DOULBLE SLIT EXPERIMENT THE INTENSITY AT CENTRAL MAXIMUM IS I. THE INTENSITY AT A DISTANCE B/4 AT CENTRAL MAXIMUM IS ( B IS THE FRINGE WIDTH)

Dear Arun Dash,

Ans: B=λD/d................(1)

Now at a distance B/4 from the central maxima the angle made by the light ray is θ, then

tanθ=B/4D≈θ≈sinθ (as θ is very small).......................(2)

Now path difference is d sinθ=d B/4D and hence phase difference is (2∏/λ)d (λD/d)/4D=∏/2

Now intensity at this point is=Icos²(∏/2)=I/2

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