What happens to the wavelength of light when it enters a denser medium?

When light enters a denser medium, such as from air into glass or water, its speed decreases due to the increased optical density of the medium. According to the relationship between wave speed, frequency, and wavelength, when the speed of a wave decreases and the frequency remains constant, the wavelength must decrease. This happens because the product of speed and wavelength equals frequency; if the speed drops while the frequency stays the same, the only way to maintain this relationship is for the wavelength to become shorter.

In the context of light, when it transitions from a less dense medium (like air) to a more dense one (like glass), you will observe that the wavelength of the light decreases as it travels through the denser material. This change is fundamental to the behavior of light and is also essential for understanding phenomena such as refraction.