When light passes from air to glass, then
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → its wavelength and velocity both decrease.
When light enters from air (rarer medium) to glass (denser medium):
→ The speed of light decreases because refractive index of glass is greater than that of air.
→ Frequency remains constant.
→ Since $v = \nu \lambda$, and $\nu$ is constant, a decrease in velocity causes wavelength to decrease.
∴ Correct answer: its wavelength and velocity both decrease.