all," the third boy said,
"if the mirror didn't face you? You've got to have the mirror
reflect right down toward your face. Then all the light that
strikes it will come down to you."

Which arrangement would work?

INFERENCE EXERCISE

Explain the following:

191. Your hands do not get wet when you put them into mercury.

192. When beating hot candy, we sometimes put it in a pan of
water.

193. Electric stoves frequently have bright reflectors.

194. We put ice in the _top_ of a refrigerator.

195. You can jack up the back part of an automobile when you
could not possibly lift it up.

196. The sun shines up into your face and sunburns you when
you are on the water.

197. People in the tropics dress largely in white.

198. Menthol rubbed into your skin makes it feel very cold
afterward.

199. We feel the heat of the sun almost as soon as the sun
rises.

200. You can shoot a stone far and hard with a sling shot.

SECTION 23. _The bending of light: Refraction._

How do glasses help your eyes?

On a hot day, how is it that you see "heat waves" rising from
the street?

What makes the stars twinkle?

Light usually travels in straight lines. If the light from an object
comes from straight in front of you, you know that the object is
straight in front of you. But you can bend light so that it seems to
come from a different place, thus making things seem to be where they
are not.

EXPERIMENT 44. Hold a triangular glass prism vertically
(straight up and down) in front of one eye, closing the other
eye. Look through the prism, turning it or your head around
until you see a chair through it. Watch only the chair through
the prism. When you are sure you know just where it is, try to
sit down in it.

Now look for a pencil or a piece of chalk through the prism,
in the same way. When you think you know where it is, try to
pick it up.

The reason the chalk and chair seem to be where they are not is that
the prism bends the light that comes from them and makes the light
seem to come from somewhere else.

As you already know, when you look at a chair you see the light that
reflects from it. You judge where the chair is by the direction from
which the light is coming when it reaches your eye. But if the light
is bent on its way, so that it comes to your eye as it ordinarily