EM waves for communication

• Absorption of Radio Waves:
• When radio waves are absorbed by a conductor, such as an antenna, they induce an alternating current (AC) at the same frequency as the incoming radio waves. This allows the signal to be received and processed by radios, televisions, and other communication devices.
• Production of Radio Waves:
• Radio waves are generated by oscillations (vibrations) in electrical circuits. When an alternating current (AC) is applied to an antenna, it causes electrons to oscillate, which generates radio waves that can travel through the air and other mediums.

Transmission and Reception of Radio Waves

Transmitters:

• A transmitter is a device in which electrons oscillate to produce radio waves.

Uses of Radio Waves

• Radio waves are mainly used for communication and broadcasting.

Long Wave Radio

• Wavelength: 1–10 km.
• Can be received from halfway around the world because long wavelengths bend around the curved surface of the Earth.
• This means you can receive a signal even if the receiver isn't in direct sight of the transmitter.

Short Wave Radio

• Wavelength: 10–100 metres.
• These signals can travel long distances because they are reflected by the Earth's atmosphere.

Bluetooth

• Bluetooth uses short-wave radio waves to send data between devices over short distances without wires.
  • Example: Wireless headsets.

TV & FM Radio Transmissions

• TV and FM signals use short wavelengths, so receivers must be in direct line of sight with the transmitter to get a clear signal.

Microwaves and Radio Waves for Satellites

• Both microwaves and radio waves are used for communication with satellites.
• These waves easily pass through the Earth's atmosphere.
• Microwaves are most commonly used, but some satellites also use high-frequency radio waves.

Satellite Communication (e.g., Satellite TV)

1. A signal from a transmitter is sent into space.
2. A satellite receiver orbiting the Earth picks up the signal.
3. The satellite transmits the signal back to Earth, but in a different direction.
4. The signal is received by a dish on the ground.