Question
Two slits spaced 0.25 mm apart are placed at 0.75 m from a screen and illuminated by coherent light with a wavelength of 650 nm. The intensity at the centre of the central maximum (θ=0∘) is I0. The distance on the screen from the centre of central maximum to the point where the intensity has fallen to I02 is nearly
Answer: Option D
:
D
I=I0cos2(πdsinθ)λ=I02
cos(πdsinθλ)=1√2
we get,
x=λD4d=650×10−9×0.754×0.25×10−3=487.5×10−6m
=0.4875mm=0.5mm
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:
D
I=I0cos2(πdsinθ)λ=I02
cos(πdsinθλ)=1√2
we get,
x=λD4d=650×10−9×0.754×0.25×10−3=487.5×10−6m
=0.4875mm=0.5mm
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