Radio waves are produced by accelerated motion of charges in a conducting wire.

The frequency of waves produced by the circuit depends upon the magnitudes of the inductance and the capacitance (This will be discussed in XIIth standard).

Thus, by choosing suitable values of the inductance and the capacitance, radio waves of desired frequency can be produced.

Properties

1) They have very long wavelengths ranging from a few centimetres to a few hundreds of kilometres.

2) The frequency range of AM band is 530 kHz to 1710 kHz. Frequency of the waves used for TV-transmission range from 54 MHz to 890 MHz, while those for FM radio band range from 88 MHz to 108MHz.

Notation used for high frequencies

1 kHz = one kilo Hertz =1000 Hz = 10^3 Hz

1 MHz = one mega Hertz = 10^6 Hz

1 GHz = one giga Hertz =10^9 Hz

Notation used for small wavelengths

1 m = one micrometer = 10^-6 m

1 Å= one angstrom = 10^-10 m= 10^-8 cm

1nm = one nanometer = 10^-9 m

Uses

1) Radio waves are used for wireless communication purpose.

2) They are used for radio broadcasting and transmission of TV signals.

3) Cellular phones use radio waves to transmit voice communication in the ultra high frequency (UHF) band.