Final answer:
The speed of a light ray decreases as it passes from air to glass to water due to the increasing optical density of each medium. Consequently, the speed of light in air is greater than in water, which is greater than in glass. Additionally, light refracts towards the perpendicular when entering a denser medium and away when entering a less dense medium.
Step-by-step explanation:
When a light ray passes through different media, such as from air through glass into water, its speed changes according to the optical density of the media. Air, having the lowest optical density, allows light to travel at a speed closest to its speed in a vacuum. As the light enters the glass, which is denser than air, its speed decreases. Further, when the light moves from glass into water, its speed changes again, depending on the relative optical densities of glass and water.
Given that the index of refraction of air (n = 1.0003) is less than that of water (n ≈ 1.33) and both are less than that of crown glass (n=1.52), we can deduce that the speed of light in air > the speed of light in water > the speed of light in glass. This happens because light travels slower in media with a higher refractive index due to more interaction with the material's molecules, which causes the light to 'slow down' in a given medium.
When it comes to direction, the light will refract, or change direction, toward the perpendicular when it goes from a less dense medium to a denser one, such as from air to water or water to glass. Conversely, it will refract away from the perpendicular when it travels from a denser to a less dense medium, like from glass to air.