We can illustrate the movement of sound waves quite simply by studying something we have all done at some time - dropping a stone into a pond.  A stone dropped into a smooth pond causes little ripples - or waves - to radiate out from the centre....

Illustration: Wave motion, and how a wave is measured If study waves on water, it will help us to understand radio waves, always remembering that radio waves travel at 186,000 miles a second in ether (something which is supposed to be in...

Heinrich Hertz proves that radio waves could be created Eight more year passed before a German, Heinrich Hertz, made an experiment which proved Maxwell had been right.  Hertz used simple apparatus - just two Leyden jars. A Leyden jar is a...

Whilst the television camera is picking up the picture, we must have some means of picking up the voices of the actors or commentators and all the other sounds connected with the scene being televised. The camera's job is to turn the sound into...

Before the radio was invented people used diverse ways of communication and signals. Here is a flag signal semaphore chart widely adopted and used in the maritime world in 19th and at the beginning of 20th Century.  Illustration: The story of...