A ray of light passes from air to glass. Which quantity remains unchanged? MCQ with Answer and Explanation

When light crosses media, frequency remains constant as it's determined by the source. Speed and wavelength change proportionally: v = fλ, and v = c/n, so λ decreases in denser medium (glass). Amplitude may change due to reflection/transmission coefficients. Memory aid: 'Frequency is source-dependent; speed and wavelength are medium-dependent'. This fundamental wave property is frequently tested in refraction questions. Competitive exams often use this to assess understanding of wave behavior at interfaces. Always recall that color (frequency) doesn't change during refraction, though speed and wavelength do.