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Question:

While conducting the Young's double slit experiment, a student replaced the two slits with a large opaque plate in the x-y plane containing two small holes that act as two coherent point sources(S1,S2)emitting light of wavelength 600 nm. The student mistakenly placed the screen parallel to thex−zplane (forz>0) at a distanceD=3m, from the mid-point ofS1,S2, as shown schematically in the figure. The distance between the sourcesd=0.6003mm. The origin O is at the intersection of the screen and the line joiningS1,S2. Which of the following is(are) true of the intensity pattern on the screen?

The region very close to the point O will be dark

Hyperbolic bright and dark bands with foci symmetrically placed about O in the x-direction.

Semi circular bright and dark bands centered at point O

Straight bright and dark bands parallel to the x-axis

Solution:

Fringes will be semi circular from YDSE theory.dλ=1000+12At O,Δx=1000λ+λ2Hence it will be dark at O.Answer is A and B.