The Matchbox Telephone One day a telephone fitter came and started installing a telephone. When he had finished the job, Lenya said, looking at the brand new telephone: "I wish we had one like that!" "But who did I just install this telephone for? Now this telephone is yours." "We don't need one like that. We need our own, so that Irishka can call from the factory to the hospital." "And where are the hospital and factory?" asked the fitter with interest. "The hospital is on the sofa," said Lenya, "and the factory is in our room." "I see..." the fitter thought for a moment. "Do you have matches?" "Yes!" "And thread?" "We have thread too." "Bring them here!" The fitter threaded a needle with thread, then emptied the matches out of the box and pierced its bottom with the needle. After that, he pulled the thread out of the needle. And so that the end of the thread wouldn't slip out of the box, he tied a match to it. To the second end of the thread, the fitter attached a second matchbox in exactly the same way. When he finished this work, he gave both boxes to the children and said: "You, Irinushka, stand here, and you, Lenya, go to your factory." Irishka took her box and waited, while Lenya ran to the children's room. There he stopped, and the thread between the boxes was pulled taut like a string. Lenya put his box to his lips, and Irishka put hers to her ear. "Irishka, can you hear me?" "I can hear you just fine even without the telephone." "Close your other ear with your hand," said the fitter. Irishka covered her other ear with her palm. "Irishka!" Lenya shouted again. "Now I can hear well through the telephone," said Irishka, and she put her box to her lips. "Lenya... Oh!" "What is it?" asked the fitter. "It's tickling my finger," said Irishka. "And what's tickling it?" "The bottom of the box," said Irishka. "So it's vibrating?" asked the fitter. "Yes," agreed Irishka. "The bottom vibrates and makes the thread vibrate," added the fitter. "I know!" shouted Lenya. "What do you know?" the fitter asked with interest. "The vibration runs along the thread to my box and makes its bottom vibrate, and from that, sound is produced again." "That's right. Well, and when we talk without the matchbox telephone, how does the sound of my voice reach your ear? After all, there's no thread, so what vibrates?" The children thought about it. They thought and thought, and then Irishka said: "You know, it's the air that vibrates. Put your fingers to your throat." The fitter did so. "Now say 'ahhh.'" "A-a-a," said the fitter. "Do you feel your throat vibrating?" "I do." "Well, when we speak, our throat vibrates, and it makes the air start vibrating, and from that, waves travel through the air, like on water, except in air you can't see them, but you can hear them." "Well, well done," said the fitter and smiled at the children as he left. --- Try it yourself! Make a telephone from thread and matchboxes. Talk to someone on this telephone, and then touch the thread with your finger. Will they hear you? Why doesn't the sound reach the second box if you touch the thread with your finger? --- When making a toy telephone, you need to keep in mind that the thread stretched between the two boxes must not touch any objects, including the fingers holding the box. You should explain to children that if the thread touches any object, the vibration of the thread is transferred to that object and no longer travels further. That's why no sound is heard in the second box. Instead of matchboxes, you can use any other suitable-sized boxes: from face powder, tooth powder, or paper clips. One boy wrote that he used thin wire without soft insulation, forty meters long, instead of thread. He did this experiment with friends on the street, and it was very audible. You can show children that sound travels not only through thread but also through other media. For instance, if you dive into a pool, lowering your head into the water so that your ears are submerged, you can hear the sound of people splashing nearby, a motorboat working far away, and so on. Sound travels well through metals. To verify this, you can tap on a heating radiator. In an adjacent apartment, this sound will be heard very clearly. Of course, you shouldn't overdo this experiment, since the sound through the pipes travels not only to the apartment you want, but to all the other apartments as well. An interesting experiment was described in a letter from one girl. Her mother dropped a pebble into a bathtub filled with water, and the girl, pressing her ear to the side of the tub, listened as the waves spreading in circles began to crash against the tub's walls. This created a vivid illustration of how sound waves propagate and reach the ear. It's important to note that in this experiment, the child will hear the sound of the falling pebble twice. First, she will hear the sound that was transmitted by sound waves, which in water, just as in air, are invisible and travel at high speed. Then the child will see the ordinary waves on the water's surface, which spread in circles in all directions from where the pebble fell, and finally, when these waves reach the tub's wall, she will hear them. You should explain to the child that real sound waves in water, as in air, are invisible, and we did the experiment with waves on the water's surface so as to better understand how sound propagates in all directions through air, water, and other media.