How do radiowaves work?

Question

How do radiowaves work?

Answer 1

Radio waves have the longest wavelengths in the electromagnetic spectrum. These waves can be longer than a football field or as short as a football. Radio waves do more than just bring music to your radio. They also carry signals for your television and cellular phones. The antennae on your television set receive the signal, in the form of electromagnetic waves, that is broadcasted from the television station. It is displayed on your television screen.

Cable companies have antennae or dishes which receive waves broadcasted from your local TV stations. The signal is then sent through a cable to your house.

Because radio waves are larger than optical waves, radio telescopes work differently than telescopes that we use for visible > light (optical telescopes). Radio telescopes are dishes made out of conducting metal that reflect radio waves to a focus point. Because the wavelengths of radio light are so large, a radio telescope must be physically larger than an optical telescope to be able to make images of comparable clarity. For example, the Parkes radio telescope, which has a dish 64 meters wide, cannot give us any clearer an image than a small backyard telescope!

In order to make better and more clear (or higher resolution) radio images, radio astronomers often combine several smaller telescopes, or receiving dishes, into an array. Together, the dishes can act as one large telescope whose size equals the total area occupied by the array.

Hope it helped. =]

Answer 2

At one instance in time, a transmitter places a potential difference (voltage) on an antenna with respect to the ground.

At another instance, a different potential is placed on the antenna.

A changing voltage causes a changing electric field.

When you've got a time varying electric field, you'll also get a time varying magnetic field.

Regardless of the distance, any charged particle will be influenced by both changing fields, and will respond by moving in a conductor such as in a receiving antenna, creating a corresponding voltage and current.

So, if you generate a varying EM field somewhere, you can detect it somewhere else.

Bear in mind, though, that the power received will decrease proportionally to the square of the distance between the two antennas.