Q. The wavelength of red light from He-Ne laser is 633nm in air but 474 nm in the aqueous humor inside the eye ball. Then the speed of red light through the aqueous humor is
A) $3\ \times \ 10^{8}{ms}^{- 1}$
B) $1.34 \times \ 10^{8}{ms}^{- 1}$
C) $2.25 \times 10^{8}{ms}^{- 1}$
D) $2.5 \times 10^{8}{ms}^{- 1}$
Explanation
(c) $\frac{Speed\ of\ light\ in\ air}{Speed\ of\ light\ in\ aqueous\ humor}$
$= \frac{Wavelength\ of\ light\ in\ air}{Wavelength\ of\ light\ in\ aqueous\ humor}$
$\Rightarrow \frac{v_{1}}{v_{2}} = \frac{\lambda_{1}}{\lambda_{2}}$
Or $v_{2} = \frac{\lambda_{2}}{\lambda_{1}} \times v_{1} = \frac{474}{633} \times 3 \times 10^{8}$
$\ \ \ \ \ \ \ \ \ \ \ \ = 2.25 \times 10^{8}{ms}^{- 1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.