How does the transmission of light through different mediums, such as air, water, and glass, vary in terms of speed and direction?

The speed of light varies in different mediums. In general, light travels fastest in a vacuum, then in air, followed by water, and slowest in glass. When light enters a different medium, it can change direction, a process known as refraction. The amount of refraction depends on the difference in the speed of light between the two mediums.