A source of energy, such as light or sound, which can be regarded as having negligible dimensions.
- ‘That is why we often speak of the planetary ‘disk’ in astronomy: even under slight magnification the human eye interprets a planet as a 2 dimensional source of light and not a point source.’
- ‘He also studied catacaustic curves in 1682, these being the envelope of light rays emitted from a point source after reflection from a given curve.’
- ‘Illuminance is the measurement of how bright a point source of light appears to the eye.’
- ‘Whenever an advancing wavefront of light encounters a barrier in which there is a hole, this hole acts as if it were a point source of light, with radiation of the same wavelength moving beyond the barrier away from the hole.’
- ‘Young placed a screen with two pin holes in it in front of a point source of light.’
2A localized and stationary source of pollution.Compare with non-point source
- ‘If the pesticide - toxic by definition - got into the stream, didn't the spray nozzle on the helicopter count as a point source of pollution, just like a factory pipe?’
- ‘The data show that as part of the recent economic collapse in Russia, mineral extraction activities have decreased substantially, as have the major point sources of pollution in the Lake Imandra watershed.’
- ‘The simulation showed that under still and convective conditions the vapours emitted by a point source rapidly form stationary envelopes around the leaves.’
- ‘However, in a British study in which the authors compared a population living around a point source of air pollution with a control population, no increase in the prevalence of low birth-weight was evident in the polluted area.’
- ‘He said regional council staff had concluded that the discharges would be a very high point source for several potentially toxic metals and dioxins.’
We take a look at several popular, though confusing, punctuation marks.