The Wonders of Science [antikvár]

A B.B.C. Television Outside Broadcast team may be working at a considerable distance from their base, and sometimes spare parts and replacements have to be flown to them at short notice. WIRELESS AND TELEVISION An Explanation of Hew They Work IF Julius Caesar or Sir Walter Raleigh could spend a day or two in our modern world, they would marvel at the sight of people riding around in buses nearly as big as a house, at great man-carrying " birds," filling the sky with the thunder of their jet-engines, and at the way a room can be lighted in an instant by the flick of a switch. But none of these things would astound them so much as the small radio and television sets that stand in the corner of a room in your home. Most of you will have been hstening to the wireless or watching TV for as long as you can remember. You probably take them for granted, as part of your daily life, without ever stopping to think how wonderful it is that we can produce music and moving pictures out of thin air. You know that there is nothing magical about either radio or television; but do you know how they work? If not, try to remember what happened last time you threw a stone into a river or pond Circular ripples flowed out from where the stone entered the water, growing larger and larger until they either hit the edge of the water or faded away. Sound and light both travel in waves, in the same way as ripples, except that their waves are very much closer together and travel very much faster. SOUND WAVES We cannot normally see sound waves, which is just as well because the air is full of them all the time. When you bang a drum, for example, the parchment drumhead vibrates at the rate of a few dozen times a second, creating pressure waves in the surrounding air. These waves travel outwards ir> all directions, hke ¦W.O.S.