Answer: Refraction
Explanation:
Refraction is the bending of light as it passes from one medium into another (ie. air to water, water to air).
We need light in order to see. When we look at the glass outside of the glass of water, the light coming from the glass travels through the air straight to your eye. As you look at the glass in the glass of water, the light coming from the straw to your eye bends as it passes through three different mediums (water, glass, and air). As the light passes from one medium to the next, it changes speed and bends.
