Here's how it works:
* Light travels at different speeds in different mediums. Light travels faster in air than it does in water.
* When light passes from one medium to another, it bends. This bending is called refraction.
* The angle of refraction depends on the angle at which the light enters the new medium.
When you look at a rock underwater, the light rays from the rock travel through the water and then into the air, where they reach your eyes. Because light bends as it passes from water to air, the path of the light rays is altered. This makes the rock appear to be in a slightly different position than it actually is.
Here's a simple analogy: Imagine you're looking at a straw in a glass of water. The part of the straw that's submerged in water appears to be bent at the surface. This is because the light rays from the straw are bent as they travel from the water to the air.
The greater the difference in the speed of light between the two mediums, the greater the angle of refraction. This is why the apparent shift in the rock's position is more noticeable when looking at it from a greater depth.
