Inference Exercise
Explain the following:
201. The fire in the open fireplace ventilates a room well by making air go up the chimney.
202. A drop of water glistens in the sun.
203. Dust goes up to the ceiling and clings there.
204. When you look at a person under moving water, his face seems distorted.
205. You sit in the sun to dry your hair.
206. Paste becomes hard and unfit for use when left open to the air.
207. In laundries clothes are partly dried by whirling them in perforated cylinders.
208. Circus balloons are filled by building a big fire under them.
209. Unevenness in a window pane makes telephone wires seen through it look crooked and bent.
210. You can see the image of a star even in a shallow puddle.
Fig. 69. When the light from one point goes through the lens, it is bent and comes together at another point called the focus.
Section 24. Focus.
How can you take pictures with a camera?
What causes the picture in the camera to be inverted?
Why is a magnifying glass able to set things on fire when you let the sun shine through it?
In your eye, right back of the pupil, there is a flattened ball, as clear as glass, called the lens. If the lens were left out of your eye, you never could see anything except blurs of light and shadow. If you looked at the sun it would dazzle you practically as much as it does now. However, you would not see a round sun, but only a blaze of light. You could tell night from day as well as any one, and you could tell when you stepped into the shade. If some one stepped between you and the light, you would know that some one was between you and the light or that a cloud had passed over the sun,—you could not be quite sure which. In short, you could tell all degrees of light and dark apart nearly as well as you can now, but you could not see the form of anything.
