InterviewSolution
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InterviewSolution
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Two waves of light in air have the same wavelength and are intially in phase. They then travel through plastic layers with thickness of `L_(1) = 3.5 mm` and `L_(2) = 5.0 mm` and indices of refraction `n_(1) = 1.7` and `n_(2) = 1.25` as shown in figure. The rays later arrive at a common point. The longest wavelength of light for which constructive interference occurs at the point is A. `0.8 mu m`B. `1.2 mu m`C. `1.7 mu m`D. `2.9 mu m` |
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Answer» Correct Answer - b `Delta x = `path difference between two light waves `= [n_(1) L_(1) + L_(2) - L_(1)] - [n_(2) L_(2)]` `Delta phi =` phase difference between two waves For longest wavelengths, `Delta phi` is the smallest. For constructive interference, `Delta phi = 2 pi` `I_(max) = n_(1) L_(1) - n_(2) L_(2) + (L_(2) - L_(1))` `(1.7) (3.5 xx 10^(-6)) - (1.25) (5.0 xx 10^(-6))` `+ (5.0 - 3.5) xx 10^(-6)` ` = (5.95 - 6.25 + 1.5) xx 10^(-6) = 1.2 5 10^(-6)m` `= 1.2 mu m` |
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