Point source

A point source is a single identifiable localized source of something. A point source has negligible extent, distinguishing it from other source geometries. Sources are called point sources because in mathematical modeling, these sources can usually be approximated as a mathematical point to simplify analysis.

Radio waves
Radio wave sources which are smaller than one radio wavelength are also generally treated as point sources. Radio emissions generated by a fixed electrical circuit are usually polarized, producing anisotropic radiation. If the propagating medium is lossless, however, the radiant power in the radio waves at a given distance will still vary as the inverse square of the distance if the angle remains constant to the source polarization.

Examples:


 * Radio antennas are often smaller than one wavelength, even though they are many metres across
 * Pulsars are treated as point sources when observed using radio telescopes

Sound
Sound is an oscillating pressure wave. As the pressure oscillates up and down, an audio point source acts in turn as a fluid point source and then a fluid point sink. (Such an object does not exist physically, but is often a good simplified model for calculations.)  Examples:


 * Seismic vibration from a localised seismic experiment searching for oil
 * Noise pollution from a jet engine in a large-scale study of noise pollution
 * A loudspeaker may be considered as a point source in a study of the acoustics of airport announcements