Q. Refractive index of air is 1.0003. The correct thickness of air column which will have one more wavelength of yellow light ($6000\ \mathring{\mathrm{A}}$) than in the same thickness in vacuum is
A) $2\ mm$
B) $2\ cm$
C) $2\ m$
D) $2\ km$
Explanation
(a) For vacuum $t = n\ \lambda_{o}$ …(i)
For air $t = (n + 1)\lambda_{a}$ …(ii)
From equation (i) and (ii)
$t = \frac{\lambda}{\mu - 1} = \frac{6 \times 10^{- 7}}{1.0003 - 1}\left( \mu = \frac{\lambda_{o}}{\lambda_{a}} \right)$
$= 2 \times 10^{- 3}m = 2mm$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.