IIT JEE , AIEEE Forum - Physics , Optics

rakesh61

if 2 coherent sources are placed at a distance 3L from each other symmetric to the center of the circle shown R>> L

then the nos of bright fringes shown on the screen placed along the circumference is

Ans 12

Please give detailed solutions rates assured for satisfactory ans

nikhil_creating_destiny

for a bright point the path diff. at point must be integral multile of L. If u consider the positions on cicumference there are 2 equtorial & 2 axil positoins w.r.t. sources.

now it is sure that at equtorial positions the path diff. is zero.

also at both axil positions path diff. is 3L.as in both the cases it is integral multiple of L these 4 positions are bright.

now from equtorial to it's adj. axil positions phath diff. varies from 0 to 3L hence there points inbetween these 2 points where path diff. is L&2L .these 2 points will also be bright.

now path diff. at any point cannot exceed 3L.hence there are total 12 points [2 having path diff. 0, 4 having path diff. L, 4 having path diff. 2L, 2 having path diff.3L] on circumferece which are bright.

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