Radio Waves

Radio waves are made by oscillating charges

EM waves are made up of oscillating electric and magnetic fields
Alternating currents are made up of oscillating charges. As the charges oscillate, they produce oscillating electric and magnetic fields
The frequency of the waves produced will be equal to the frequency of the alternating current
You can produce radio waves using an alternating current in an electrical circuit. The object in which charges oscillate to create the radio waves is called a transmitter
When transmitted radio waves reach a receiver, the radio waves are absorbed
The energy carried by the waves is transferred to the electrons in the material of the receiver
This energy causes the electrons to oscillate and, if the receiver is par5t of a complete electrical circuit, it generates an alternating current

Radio waves are EM radiation with wavelengths longer than about 10cm
Long-wave radio can be transmitted from London, say, and received halfway round the world. That’s because long wavelengths diffract around the curved surface of the Earth. Long-wave radio wavelengths can also diffract around hills, into tunnels and all sorts
This makes it possible for radio signal to be received even if the receiver isn’t in line of the sight of the transmitter
Short-wave radio signals can, like long-wave, be received at long distances from the transmitter. This is because they are reflected from the ionosphere, an electrically charged layer in the Earth’s upper atmosphere
Bluetooth uses short-wave radio waves to send data over short distances between devices without wires
Medium-wave signal can slo reflect from the ionosphere, depending on atmospheric conditions and the time of day
The radio waves used for TV and FM radio transmission have very short wavelengths. To get reception, you must be in direct sight of the transmitter-the signal doesn’t bend or travel far through buildings