Refraction of Light.
How do the rays of light from the sun come to us?
They come to us in straight lines.
When the rays of light pass from one substance to another more dense, what takes place?
They are bent or turned from a straight course.
What is said of these bent rays?
They are said to be refracted.
What is meant by refraction?
Bending a ray of light, as it passes from one substance to another of different density; as from air to water, or from water to air.
Where may we see an example of refraction?
In the rays of light from a rod which has one end in the water.
Fig. 7.
Why does the rod appear to be bent?
Because light coming from the part of the rod under the water, is refracted or bent at the surface of the water, while the light from the part above the surface, comes in straight lines to the eye; hence, the rod appears to be bent at the surface, as is represented in [Fig. 7].
How does a pole appear when one end is placed in the water?
It appears to be bent where it meets the surface of the water.
How does the part of the rod under water appear?
The part under the water appears to be raised up, as may be seen in [Fig. 7].
How does the bottom of a pond or stream of water appear?
It appears to be raised up, and the water does not seem so deep as it really is.
Why is this the case?
Because the light from the bottom of the pond is refracted or bent at the surface of the water; hence, the bottom appears to be raised up.
How much does the bottom of a pond or stream of water seem to be raised up?
About one-third of the depth of the water.
If the water is really six feet deep, how deep does it appear?
It appears to be only four feet deep.
What has frequently happened from not knowing this fact?
People have been drowned from getting into water deeper than it appeared to be.
Do the fish and other things floating in the water appear to be raised up?
Yes; like the bottom of the stream, they also appear to be only two-thirds as far from the surface as they really are.
If we wish to spear the fish, what must we do?
We must aim below the place where they seem to be, or we must strike perpendicularly at them.