Radio waves

Radio waves can be submitted through satellites and space

  1. Radio waves have the longest wavelengths in the electromagnetic spectrum. They range from the length of a football to larger than our planet. Heinrich Hertz proved the existence of radio waves in the late 1880s. He used a spark gap attached to an induction coil and a separate spark gap on a receiving antenna. When waves created by the sparks of the coil transmitter were picked up by the receiving antenna, sparks would jump its gap as well. Hertz showed in his experiments.

elctro magnetic waves

Of all of the types of elcetro magnetic radiation, radio waves have the lowest frequency and the longest wavelength. The atmosphere of the Earth is transparent to radio waves with wavelengths of a few millimetres to about twenty metres. As such radio telescopes can be ground based. Radio telescopes consist of very large dishes constructed of metal plates which focus the radio waves to a point above the centre of the dish where the receiver is located. Radio telescopes have to be very large because the long wavelengths of the EM radiation result in poor resolution. Today the majority of radio astronomy is done using interferometry which acts to mitigate the poor resolution obtained. The largest radio telescope in the world in located in Arecibo, Puerto Rico. It is 300 metres in diameter and is constructed in a natural bowl shaped depression.
Radio astronomy began in the1930s but did not really take off until after the Second World War. Numerous sources of radio waves have been detected such as radio galaxies and quasars as well as emssions from the centre of the Milky Way Galaxy.