InterviewSolution
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InterviewSolution
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White light is incident normally on a glass plate of thickness `0.50 xx 10^(-6)` and index of refraction 1.50. Which wavelengths in the visible region `(400 nm - 700 nm)` are strongly reflected by the plate? |
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Answer» The light of wavelength `lambda` is strongly reflected if `2 mu d = (n + (1)/(2)) lambda` Where n is a non-negative integer. Here `2 mu d = 2 xx 1.50 xx 0.5 xx 10^-6 m = 1.5 xx 10^-6 m`. Putting `lambda = 400` nm in Eq.(i), we get `1.5 xx 10^-6 m = (n + (1)/(2)) (400 xx 10^-(6) m)` or ` n = 3.25` Putting `lambda = 700 nm` in Eq. (i), we get `1.5 xx 10^(-6) m = (n + (1)/(2)) (700 xx 10^(-9) m)` or `n = 1.66` Thus, within 400 nm to 700 nm, the integer n can take the values 2 and 3. Putting these values of n in (i), the wavelengths become ` lambda = (4 mu d)/(2 n + 1) = 600 nm and 429 nm` Thus, light of wavelenghts 429 nm and 600 nm are strongly reflected. |
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