Effects of Refraction. Whenever a straight stick is placed in water at an angle, as AB (Fig. 1), it appears bent at the surface of the water D, the part BD below the surface seeming to rise, the end B taking the position C. This effect is due to the refraction of the ray BF at F, where it takes the direction FE, and to the fact that the apparent position of a body is in the direction of the ray that enters the eye.
For the same reason a pond into which one looks seems to be shallower than it really is. to be shallower than it really is.
Refraction takes place in gases also, when rays pass from one medium into another of different density. This gives rise to two effects at sunrise and sunset.
First. -The sun is seen when it is really below the horizon. If the line AB (Fig. 2) represents the horizon at the point A, the sun, though below it, at the point S, appears to be at the point S': for the rays from S, on striking the atmosphere of the earth and constantly passing into denser layers, are bent downward, and as the ray that enters the eye is from the direction S'A, this makes the sun appear to be at S'.
Second. -Another effect is that upon the apparent shape of the sun. The rays that are nearest the horizon are bent the most, so that the lower side appears higher than it really is, with reference to the upper side. This causes an apparent flattening of the sun near the horizon, especially on the lower side.
