The central fringe of interference pattern produced by light of wavelength 6000Å is found to shift to the position of 4th bright fringe, after a glass plate of μ=1.5 is introduced. The thickness of the glass plate is:
A
4.8μm
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B
8.23μm
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C
14.98μm
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D
3.78μm
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Solution
The correct option is A4.8μm We know, Shift at nth bright fringe is (μ−1)t=nλ Given, μ=1.5 n=4 λ=6000Å So, (1.5−1)t=4(6000×10−10) t=4.8×10−6m ⇒t=4.8μm So, option (a) is correct.