in radiology, a measure of the ability of a medium to absorb radiation, expressed as the logarithm of the quotient of the intensity of the radiation entering the medium divided by that leaving it.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
ab·sor·bance (A, A), (ab-sōr'bants),
spectrophotometry log of the ratio of the radiant power of the incident radiation to the radiant power of the transmitted radiation.
Farlex Partner Medical Dictionary © Farlex 2012
Absorbance Chemistry A logarithm of the percent transmission of a wavelength of light through a liquid.
Microbiology A measure of the amount of light absorbed by a suspension of bacteria or an organic solution, measured by spectrophotometry. Absorbance values are used to plot the growth of bacteria in broth and gauge the purity and concentration of molecules in solution.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.
2 minus the log of the percentage transmittance of light.
(2) , optic density
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
absorbance a spectrophotometric measurement of the light absorbed by a solution at a particular WAVELENGTH. The absorbance (A) derives from the percentage of light transmitted as follows:
where Io is the incident light intensity and I is the transmitted light intensity. The absorbance is related to the molar absorption coefficient (extinction coefficient) e (cm-1M-1), concentration c (M), and path length l (cm) as follows:
Absorbance can therefore be used to determine the concentration of a substance in solution, to follow conversion of a SUBSTRATE to a product in an enzymic reaction (see ENZYME), and so on.
Absorbance is sometimes referred to as OPTICAL DENSITY, although this term should be used for measurement of light scattering.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
A measure of absorption equal to the logarithm to the base 10 of the reciprocal of the transmittance T
, for a specified wavelength and expressed as A
= −log10 T
. optical density. See optical density
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann