When a ray of light enters from a rarer medium to a denser medium at an angle other than normal incidence, how does its speed and wavelength change?

💡 Solution & Explanation

When light travels from an optically rarer medium to a denser medium, its frequency remains unchanged because it depends strictly on the source, but the velocity of propagation decreases. Since velocity equals the product of frequency and wavelength, a decrease in speed directly results in a proportional decrease in wavelength. Incorrect options assume wave properties change independently or that frequency shifts during refraction. The refractive index of a medium is defined as the ratio of the speed of light in vacuum to that in the medium.