When light enters from air into glass, which of the following quantities changes?
Correct: C
When light passes from one transparent medium to another (e.g., from air to glass), its speed changes, causing its wavelength to also change. However, the frequency of light, which is determined by its source, remains constant during refraction. The relationship is given by v = fλ, where v is speed, f is frequency, and λ is wavelength.