How Refraction Deceives us

Refraction:
Refraction is the source of many illusions; bent rays of light make objects appear where they really are not. A fish at A seems to be at B. The end of the stick in Figure 64 seems to be nearer the surface of the water than it really is.

The light from the sun, moon, and stars can reach us only by passing through the atmosphere, but in Section 76, we learned that the atmosphere varies in density from level to level; hence all the light which travels through the atmosphere is constantly deviated from its original path, and before the light reaches the eye it has undergone many changes in direction. Now we learned in Section 102, that the direction of the rays of light as they enter the eye determines the direction in which an object is seen; hence the sun, moon, and stars seem to be along the lines which enter the eye, although in reality they are not.

FIG. - A fish at A seems to be at B.