Editing Turbidity (section)

{{Short description|Cloudiness of a fluid}}
{{Redirect|Turbid}}
[[File:TurbidityStandards.jpg|thumb|Turbidity standards of 5, 50, and 500 NTU]]
{{Pollution sidebar|Water}}
'''Turbidity''' is the cloudiness or [[haze|haziness]] of a [[fluid]] caused by large numbers of individual [[Particle (ecology)|particles]] that are generally invisible to the [[naked eye]], similar to [[smoke]] in air. The measurement of turbidity is a key test of both [[water clarity]] and [[water quality]].

Fluids can contain suspended solid matter consisting of particles of many different sizes. While some suspended material will be large enough and heavy enough to settle rapidly to the bottom of the container if a liquid sample is left to stand (the [[Settling|settable solids]]), very small particles will settle only very slowly or not at all if the sample is regularly agitated or the particles are [[colloid]]al. These small solid particles cause the liquid to appear turbid.

Turbidity (or haze) is also applied to transparent solids such as glass or plastic. In plastic production, haze is defined as the percentage of light that is deflected more than 2.5° from the incoming light direction.<ref>Thermallaminatingfilms.com. [http://www.thermallaminatingfilms.com/haze.php Haze technical definition] {{webarchive |url=https://web.archive.org/web/20150822002852/http://www.thermallaminatingfilms.com/haze.php |date=August 22, 2015 }}</ref>