Physics P1: Radio Waves and Microwaves

What can radio waves be used for?

Radio waves are used to broadcast TV and radio signals and to transmit satellite signals in the same way as microwaves.

What can microwaves be used for?

Microwaves can be used for satellite communication and also mobile phones. Communication to and form satellites including satellite TV signals and satellite phones use microwaves. But you need to use microwaves which can pass easily through the Earth's watery atmosphere.

Why do microwave ovens use a different microwave wavelength from satellites?

In communications, the microwaves used need to pass through Earth's watery atmosphere. In microwave ovens, the microwaves need to be absorbed by water molecules in food to be able to heat it up so they use a different wavelength to those used in satellite communications. The microwaves penetrate up to a few centimeters into the food before being absorbed by water molecules. The energy from the absorbed microwaves causes the food to heat up. The heat energy is then conducted or transported to other parts of the food.

What is the ionosphere

The layer of the earth's atmosphere which contains a high concentration of ions and free electrons and is able to reflect radio waves. It lies above the mesosphere and extends from about 80 to 1,000 km above the earth's surface.

How can short-wave radio signals transmit like long waves and be received at long distances from the transmitter?

They have a wavelength of 10 m - 100 m, these radio waves are reflected from the ionosphere, which is an electrically charged layer in the Earth's upper atmosphere Medium wave signals can also reflect from the ionosphere depending on atmospheric conditions and time.