What occurs to light when it moves from glass back to air?

When light moves from glass back to air, it speeds up. This phenomenon occurs due to the difference in the optical densities of the two media. Light travels slower in denser materials, such as glass, compared to less dense materials, like air.

When transitioning from glass (a medium with a higher refractive index) to air (with a lower refractive index), the light waves gain speed because they are moving into a medium that offers less resistance to their transmission. This change can be observed as a change in the light's wavelength as well, although the frequency remains constant.

The interaction at the boundary between the two media can also lead to other behaviors, such as reflection or bending, but in this case, the fundamental effect is the increase in the speed of light as it exits the denser medium.