InterviewSolution
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InterviewSolution
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Find the maxinum intensity in case of interference of n identical waves each of intensity `I_(0)` if the interference is (a) coherent and (b) incoherent. |
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Answer» The resultant intensity is given by `I = I_(1) + I_(2) + 2 sqrt( I_(1) I_(2)) cos phi` a. The sources are said to be coherent if they have constant phase difference between them. The intensity will be maximum when `f = 2 np,` the sources are in same phase. Thus `I_(max) I_(1) + I_(2) + 2 sqrt(I_(1) I_(2)) = ( sqrt I_(1) + sqrt I_(2))^(2)` Similarly, for n indentical waves, `I_(max) = (sqrt I_(0) + sqrt I_(0) + ....)^(2) = n^(2) I_(0)` b. The incoherent sources have phase difference that varies randomly with time. Thus, `[cos phi]_(av) = 0` Hence, `I = I_(2) + I_(2)` Hence, for n idental waves, `I = I_(0) + I_(0) + ... = n I_(0)` |
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