InterviewSolution
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InterviewSolution
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A parallel beam of white light is incident on a thin film of air of uniform thickness. Wavlength `7200 Å` and `5400 Å` are observed to be missing from the spectrum of reflected light viewed normally. The other wavelength in the visible region missing in the reflected spectrum isA. `6000 Å`B. `4320 Å`C. `5500 Å`D. `6500 Å` |
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Answer» Correct Answer - b The wavelength missing from the reflected spectrum must satisfy the condition,`2 mu t = n lambda`, where t is thickness of air film. `2 mu t = n lambda_(1) = (n + 1) lambda_(2)` or `n xx (7200) = (n + 1) 5400` `:.n = 3` The next wavelengths must satisfy the condidtion, `n lambda_(1) = (n + 2) lambda_(2)` or `7200 xx 3 = (3 + 2) lambda_(2) = 5 lambda_(2)` `implies lambda_(2) = 4320 Å`. |
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