WHY SMOOTH OR WET THINGS ARE SHINY. When a surface is very smooth, we say it is shiny or glossy. Even black shoes, if they are polished, become smooth enough to reflect much of the light that strikes them; of course the parts where the light is being reflected do not look black but white, as any one who has tried to paint or draw a picture of polished shoes knows. Anything wet is likely to be shiny, because the surface of water is usually smooth enough to reflect light rather directly. If a surface is uneven, like a pool with ripples on it, the light reflects unevenly, and you see a distorted image; your face seems to be rippling and moving in the water. [Illustration: FIG. 64. How should the mirror be placed?] _APPLICATION 34._ Some boys were playing war and were in a ditch that they called a trench. They wanted to make a simple periscope so that they could look out of the ditch at the "enemy" without being in danger. They had an old stovepipe and a mirror. Practically all of them agreed that if the mirror were fixed in the top of the stovepipe and if they looked up through the bottom, they would be able to see over the side of the ditch. But they had an argument as to how the mirror should be placed. Each drew a diagram to show how he thought the mirror should be arranged, using dotted lines to show how the light would come from the enemy to their eyes. Three of the diagrams are shown in Figure 64. The boy who drew the first said: "If you want to see the enemy, the mirror's got to face him. Then it will reflect the light down to your eyes." The boy who drew the second said: "No, the light would just go back to him again. The mirror must slant so that the light that strikes it at a slant will be reflected to your eye at the same slant." "How could it get to your eye at 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?