Wrap the cigarette tightly with cellophane, tighten both ends, and then tie the cigarette in a knot, which will not break or break.

If it is not wrapped in cellophane, when the cigarette is bent, the pressure is concentrated in a few places, and it will break there. Cellophane has a strong tension, which distributes the pressure evenly to the whole cigarette, so it won't break. After the knot is untied, you only need to straighten and flatten the cigarette, and it can be restored to its original appearance. Make periscope

To make a periscope, you only need a small square mirror as big as two sides and a piece of cardboard. If your small mirror is 10 cm long and 7 cm wide, you should prepare a Zhang Kuan 4×7=28 cm cardboard. The length of cardboard can be determined by itself according to the conditions. If the cardboard is longer, the periscope can be made higher.

Draw three parallel lines on the cardboard. As shown in the picture, the distance between each line is seven centimeters. Cut off the blackened part. Draw a mark along the dotted line with a knife (be careful not to cut through). Then, use the edge of the table to fold it, so as to make a rectangular box and stick it with kraft paper.

Stick the small mirror with white tape as shown below (make the angle between the small mirror and the long paper box equal to 45). Two small mirrors are parallel to each other. In this way, a periscope is made.

If the small mirror in your hand is less than 10 cm long, you can calculate the size of the carton according to the Pythagorean theorem, provided that the angle between the mirror and the carton is 45. It is very interesting to watch the scenery outside the window with periscope, and it can also be used to hide and seek. Of course, people make periscope mainly for scientific research and national defense. Scientists use periscope to observe the launch of rockets in the basement; When conducting atomic physics experiments, researchers can observe those radioactive and dangerous experiments by using periscope through a thick protective wall. When a submarine sails underwater, it must also use periscope to observe the sea surface.

Who invented the periscope? Now it is impossible to look it up. The earliest ancient book in the world that recorded the principle of periscope was Huainan Wanbi Shu in China in the second century BC. The book records such a passage: "Take a big mirror and hang it high, put a water tray under it, and you will see your neighbors."

In ancient times, under the eaves of some ancient temples in deep mountains in China, a bronze mirror was often hung obliquely. If you put a basin of water on the ground inside the temple gate, it will be the simplest periscope, and the narrow path and passers-by outside the temple gate will be reflected in the water.