So before we study the law of refraction, it is useful to discuss the speed of light and how it varies in different media. Why does light change direction when passing from one material (medium) to another? It is because light changes speed when going from one material to another. This bending of light is called refraction and is responsible for many optical phenomena.
In this case, the light can reach the observer by two different paths, and so the fish seems to be in two different places. Figure 25.10 Looking at the fish tank as shown, we can see the same fish in two different locations, because light changes directions when it passes from water to air.
