| quantum limit | The shortest wavelength found in an X-ray spectrum. (05 Mar 2000) |
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| quantum mottle | Mottle caused by the statistical fluctuation of the number of photons absorbed by the intensifying screens to form the light image on the film; faster screens produce more quantum mottle. (05 Mar 2000) |
| quantum rectum | See: Q.R. Origin: L. However much is correct (05 Mar 2000) |
| quantum requirement | The number of quanta of light absorbed required for the transformation of one molecule; the inverse of the quantum yield. (05 Mar 2000) |
| quantum satis | See: q.s. Origin: L. However much is enough Quantum sink, in radiological imaging, the stage at which statistical information reaches its lowest level because of a low photon flux. (05 Mar 2000) |
| quantum speciation | The rapid evolution of a newspecies from a small population that ispartially or totally isolated from the parent population, the rapidspeciation occurs due to geneticdrift and founder effect and usuallyinvolves a few mutations that have a big impact on the organisms' observable physical traits. (09 Oct 1997) |
| quantum sufficiat | See: q.s. Origin: L. However much is enough (05 Mar 2000) |
| quantum theory | The theory that the radiation and absorption of energy take place in definite quantities called quanta (e) which vary in size and are defined by the equation e=hv in which h is planck's constant and v is the frequency of the radiation. (12 Dec 1998) |
| quantum vis | See: q.v.. Origin: L. However much you wish (05 Mar 2000) |
| quantum yield | The number of photons required for the formation of one oxygen molecule in photosynthesis. Varies from 8-14 depending on the system used to measure it. (18 Nov 1997) |
| atomic number | <chemistry> Symbol Z. The number of protons in the nucleus of an atom and also its characteristic atomic number. The atomic numbers of the known elements form a complete series from 1 (hydrogen) to 103 (lawrencium). (16 Dec 1997) |
| Avogadro's number | <physics> The number of molecules in a mole (gram molecular weight) of a substance, equals 6.02 x 1023 molecules. (09 Oct 1997) |
| Brinell hardness number | A number related to the size of the permanent impression made by a ball indenter of specified size (usually 10 mm in diameter) pressed into the surface of the material under a specified load: where P = applied load in kg, D = diameter of the ball in mm, and d = diameter of the impression in mm. (05 Mar 2000) |
| burst number | The number of viral particles that emerge from a cell after a viralinfection has burst it open. (09 Oct 1997) |
| Mach number | A number representing the ratio between the speed of an object moving through a fluid medium, such as air, and the speed of sound in the same medium. (05 Mar 2000) |