Radio waves

How are radio waves produced ?

Produced using an alternating current (ac) in an electrical circuit .

What are alternating currents ?

They are made of oscillating charges (electrons) . As they oscillate they produce oscillating electric and magnetic field ( e.g electromagnetic waves )

What is the relationship of the frequencies of the radio wave and the alternating current ?

They are equal

What is the object in which charges oscillate to create radio waves ?

Transmitter

How are radio waves received ?

radio waves → receiver (radio waves are absorbed)

energy (carried by the waves) → (kinetic energy stores) electrons in the material of the receiver.

• electrons to oscillate

• if the receiver is part of a complete electrical circuit = alternating current

  • Hz of ac = Hz of radio wave

Commercial (general) use of radio waves ?

• radio signals (transmitter → radio aerials)

• TV signals (transmitter → TV aerials)

The use of Long-wave radio (1-10km) ?

• long wavelengths diffract (bend) around the curved surface of the earth , hills and into tunnels

  • allows radio signals to be received even if the receiver isn’t in line of sight of the transmitter

The use of Short-wave radio (10-100m) ?

(+ example)

• reflected between the earth and the ionosphere (electrically charged upper layer in the earth’s atmosphere)

  • can be received at long distances

  • Example : Bluetooth - send data over short distances between wireless devices

The use of Medium-wave radio ?

• shorter medium wave radio can be reflected from the ionosphere (depending on weather conditions)