Monday, December 24, 2012


Heat is a type of energy. It spreads from warm things to cold things. The moving molecules pass the heat along. For example, you can notice this fact if you put butter on your toast. Heat passes from the toast into the butter and causes it to melt. Altough a piece of bread is solid, it has molecules which move. When the bread is toasted, these molecules move faster.
           Cold butter also has molecules. As they are cool they move very slowly. The motion passes between the molecules until the butter becomes soft and warm. The ice cubes have very slow-moving molecules. Because the ice-cubes are very cold. On the other hand, the fruit juice has molecules with more heat energy which move faster. If we put ice in a glass of fruit juice, the molecules lose energy and move more slowly. The juice stays cool until all of the ice melts.


The radio programsa re sent by a machine called a transmitter to your radio which is called a receiver. They are sent through the air over long distances by electromagnetic waves. These are the radio waves. These were discovered by a German scientist named Heinrich Hertz. He also discovered that the radio waves have different lengths.
         Then, Guglielmo Marconi invented a microphone, that changed sound waves into electronic signals, and developed a receiver that turned them back into the sound again.
A radio wave looked like a letter –s- lying on its side. Short waves curved up and down more times each second than longer ones. He divided all the waves according to how many times they curved or how frequently they curved. He called each group a frequency.
          At last, the scientists found that they could reduce static and other noise by using only the top half of a radio wave. This transmission is called FM broadcasting.