Question

When light of wavelength 5000 Å in vacuum travels through same thickness in glass and water, the difference in the number of waves is 400. Find thickness. (Refractive indices of glass and water are `(3)/(2)` and `(4)/(3)` respectively)

Answer 1

Difference in number of waves `= (l)/(lambda)(mu_(g) - mu_(w))`
`400 = (I)/(5000 xx 10^(-10))[(3)/(2)-(4)/(3)]`
`I = 400 xx 5 xx 6 xx 10^(-7)`
`= 1.2 xx 10^(-3)m = 1.2 mm`