How does light behave when it travels from air into water?

• A. It speeds up and bends away from the normal.
• B. It slows down and bends towards the normal.
• C. It travels in a straight line without bending.
• D. It reflects off the surface of the water.

Answer: (B)

When light travels from air into water, it encounters a medium with a different optical density. In air, the speed of light is approximately 3.00 x 10^8 m/s, but when it enters water, the speed decreases to around 2.25 x 10^8 m/s. This reduction in speed causes the light to bend towards the normal, which is an imaginary line perpendicular to the surface at the point of entry.

This bending occurs due to the principle of refraction, governed by Snell's law, which describes how light changes direction as it passes between media of different densities. The change in speed is responsible for the bending of the light rays. As a result, the correct behavior is that light slows down and bends towards the normal when transitioning from a less dense medium (air) to a more dense medium (water).