Q. The wavelength of sodium light in air is $5890Å.$ The velocity of light in air is $3 \times 10^{- 8}\ ms\ \bar{}¹.$ The wavelength of light in a glass of refractive index 1.6 would be close to
A) $5890Å$
B) $3681Å$
C) $9424Å$
D) $15078Å$
Explanation
(b) When light passes from one medium to another, its frequency remains unchanged but it velocity (and hence, wavelength) changes.
$\ _{a}\mu_{g} = \frac{wavelength\ in\ air\ \left( \lambda_{a} \right)}{wavelength\ in\ glass\ \left( \lambda_{g} \right)}$
$\Rightarrow 1.6\ = \ \frac{5890}{\lambda_{g}}$
$\Rightarrow \lambda_{g} = \frac{5890}{1.6} = 3681\ \mathring{\mathrm{A}}\ $
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.