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 the x−z plane (for z>0 ) at a distance D=3m from the mid-point of S1S2, as shown schematically in the figure. The distance between the sources d=0.6003mm. The origin O is at the intersection of the screen and the line joining S1S2. Which of the following is(are) true of the intensity pattern on the screen?
(A)Straight bright and dark bands parallel to the x-axis
(B)The region very close to the point O will be dark✓ Correct
(C)Hyperbolic bright and dark bands with foci symmetrically placed about O in the x-direction
(D)Semi circular bright and dark bands centered at point O✓ Correct
Answer: (B), (D)
Solution
Since the line S1S2 is perpendicular to the screen, all points equidistant from O on the screen have the same path difference. This creates concentric semicircular fringes centered at O. ✓ (D)
