Two coherent point sources $\mathrm{S}_{1}$ and $\mathrm{S}_{2}$ are separated by a small distance 'd' as shown. The fringes obtained on the screen will be:

JEE Main · 2013 · 07 Apr 2013 · Offline · Wave Optics

Two coherent point sources

S_{1}

and

S_{2}

are separated by a small distance 'd' as shown. The fringes obtained on the screen will be:

(A)straight lines
(B)semi-circles
(C)concentric circles✓ Correct
(D)points

Answer: (C)

Solution

The two point sources lie a small distance apart, and a point on the screen belongs to a bright or dark fringe according to its path difference from the two. The set of points sharing a fixed path difference forms a surface of revolution about the line joining the sources, and where that family of surfaces cuts the screen it traces out a set of concentric circles centred on the axis. The fringes are therefore concentric circles.

JEE Main · 2013 · 07 Apr 2013 · Offline · Single correct option

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