Question

According to Huygen's principle, during refraction of light from air to a denser medium

• A. Wavelength decreases but speed increases
• B. Wavelength increases but speed decreases
• C. Wavelength and speed both increase
• D. Wavelength and speed both decrease

Answer 1

Answer: (D)

According to Huygens' principle, wavelength and speed depend on the medium in which light travels. They depend on refractive index $\mu$ of the medium. It is given by, $\mu =\frac{c}{v}$
$\therefore \mu \propto \frac{1}{v}$
Also, $v=\nu \lambda$
where, $\nu$ is frequency
$\therefore \mu \propto \frac{1}{v}\propto \frac{1}{\lambda }$ .
As refractive index of denser medium is larger, so wavelength and speed in denser medium decrease.