Radios, Televisions, Cell Phones and Electromagnetic Radiation

What do light, heat waves and radio waves have in common? Well, they are all composed of electromagnetic radiation. The radiation frequency differs, however, and light waves have a shorter wavelength than radio or heat waves. Generally, the shorter the wavelength, the harder it is for that type of electromagnetic wave to penetrate objects. For instance we find that light waves (short wavelength) will not penetrate a wall, but the longer radio waves do so with ease. This means that we cannot see a person through a brick wall (no light reflected off his or her body can reach us through a wall). Our radio can receive radio waves that pass through a wall and so our radios work inside a house even though the waves are coming from a tower outside the house.

Light waves of different frequencies give us different colours. Light waves, radio waves and heat waves all travel at the same speed in a vacuum and this speed is known as the speed of light. This speed is 300000000 metres per second which is about 8 times round the world in one second (if it travelled in such a circular manner which it does not).

When electromagnetic waves travel through conductors (such as metals) currents are set up and the electromagnetic waves are damped out (they get weaker). All transparent substances (glass, clear plastics and so on) are electrical insulators (not conductors).

Now how does a radio wave carry information? The answer is that it is modified in some way. For instance the frequency is made to change in a certain way or the amplitude of the wave is made to change in a certain way at the transmitting side. When the receiver (radio) picks up the changing wave it interprets this in a certain manner so that we can get a louder or softer sound and different pitches out of the radio.