Two parallel rays, one of red light and the other of violet light, are incident on the flat end of a $$2m$$ long glass rod. Wavelength of violet light in vacuum is $$4000$$ Ao and that of red light is $$7000$$ Ao. The mean refractive index of glass is $$1.5$$ then number of waves of violet light in the rod exceeds the number of waves of red light by

Question

Two parallel rays, one of red light and the other of violet light, are incident on the flat end of a $$2m$$ long glass rod. Wavelength of violet light in vacuum is $$4000$$ Ao and that of red light is $$7000$$ Ao. The mean refractive index of glass is $$1.5$$ then number of waves of violet light in the rod exceeds the number of waves of red light by

Infinity Learn · Accepted Answer

If l be the actual length of rod, then number of waves $$n=l$$λ$$/$$μ$$=$$μlλ∴ Percentage increase $$=nV$$−$$nRnR=$$μ$$l1$$λV−$$1$$λRμ$$l/$$λR×$$100$$%$$=$$λRλV−$$1$$×$$100$$%$$=74$$−$$1$$×$$100$$%$$=75$$%

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