1.

Consider the arrangement shownin figure. By some mechanism,the separation between the slits S_3 and S_4 can be changed. The intensity in measured at the point P which is at the common perpendicular bisector of S_1S_2 and S_3S_4. When z=(Dlamda)/(2d) the intensity measured at P is I. Find this intensity when z is equal to a. (Dlamda)/d, b. (3Dlamda)/(2d), c. (2Dlamda)/d

Answer»

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Solution :a. When `z=(lamdaD)/d`
So, `OS_3=OS_4=(lamdaD)/d`
`rarr Dark fringe at `S_3 and S_4`
`rarr At S_3` intensity at `S_3=0`
`rarrl_1=0`
At `S_4 Intensity at S_4=0`
`rarr `l_2=0`
`rarr At P PATH DIFFERENCE =0
`rarr PHASE difference =0`
`rarr l=l_1+l_2+2sqrt(l_1l_2)COSTHETA^@=0+0+0=0`
`rarr intensilty at P=0`


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