Question

A beam of monochromatic ligh first travels through glass of R.I. 1.5 and then through water (R.I. `=(4)/(3)`). If the difference in their wavelength in the two media is 40nm, then the wavelength of the monochromatic light in vacuum will be
A. `4000Å`
B. `4400Å`
C. `4800Å`
D. `5200Å`

Answer 1

Correct Answer - C
`lambda_g=I(lambda_a)/(3//2)=(2)/(3)lambda_a and lambda_w=(3)/(4) lambda_a`
`:. lambda_w-lambda_g= lambda_a[(3)/(4)-(2)/(3)]=(lambda_a)/(12)=40xx10^(-9)`
`:. ""lambda_a=12 xx 40 xx 10^(-9)=4800Å`