Radio waves

Radio waves are generated by the accelerated motion of electric charges in a conducting wire -- typically an oscillating circuit built from an inductor and a capacitor. The frequency of the radio wave produced depends directly on the magnitudes of the circuit's inductance and capacitance (the detailed circuit theory for this is developed further in Std XII), so by choosing suitable component values, a radio wave of essentially any desired frequency can be generated.

Radio waves are notable for having very long wavelengths, ranging from a few centimetres up to a few hundred kilometres. Different services are allotted their own frequency sub-bands: the AM (amplitude-modulated) radio band runs from 530 kHz to 1710 kHz, television transmission uses frequencies from 54 MHz to 890 MHz, and the FM (frequency-modulated) radio band runs from 88 MHz to 108 MHz. Radio waves are the workhorse of wireless communication generally -- used for radio broadcasting, transmission of TV signals, and (in the ultra high frequency, or UHF, sub-band) for voice communication on cellular phones. …