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Two light beams of intensities I and 4I are used to make interference pattern on a screen. Two points P and Q are marked on the screen where resultant intensities are I_P and I_Q respectively. Phase difference between the waves at point P is pi//2 and the same at Q is pi. Calculate (I_P - I_Q)//I. {:(0,1,2,3,4,5,6,7,8,9):}

Answer»


SOLUTION :Resultant intesity in terms of PHASE DIFFERENCE can be written as follows:
`I = I_1 + I_2 + 2sqrt(I_1I_2) cos DELTA`
We can use the above relation to write the FOLLOWING :
`I_P = I + 4I + 2sqrt(I xx 4I) cos pi/2 = 5I`
`I_Q = I + 4I + 2sqrt(I xx 4I) cos pi = 5I - 4I = I`
`implies I_P -I_Q = 5I - I`
`implies (I_P - I_Q)/(I) = 4`


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