(redirected from absorbances)
Also found in: Dictionary, Thesaurus, Encyclopedia.


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),

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


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.


spectrophotometry 2 minus the log of the percentage transmittance of light.
Synonym(s): extinction (2) , optic density.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


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. Syn. optical density. See optical density; transmittance.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann
References in periodicals archive ?
The absorbance is measured at the corresponding peaks after base line correction.
After [DELTA][A.sub.410] nm correction in which 5% of the absorbance of the hemoglobin peak at 410 nm was subtracted from the [DELTA][A.sub.450], mean (SD) recovery of [DELTA][A.sub.450 increased to 93 (4)% (1).
Based on these results, it can be said that the spectrum data measured at the region 1131 to 1334 nm have only one prominent source of variation, which could be equivalent to that given by the scaled absorbance at 1170 nm.
These extracts were used to investigate the relationship between absorbance at 560 nm and co-eluting protein.
Our indirect TLS absorbance system uses a 1-mW HeNe probe laser and approximately 75 mW of pump power (see accompanying box).
Therefore, the measured absorbance, A3, inside the IS can be much smaller than the true absorbance.
The absorbance of sample (methanolic extract of Nymphaea stellata and standard Butylated hydroxytoluene) were taken in triplicate.
A few minutes of exposure to an intense light source (such as that from an ordinary slide projector) eliminates most of the bilirubin absorbance and allows the absorbance present before irradiation to be determined as described in the next paragraph.
3, it is obvious that in vulcanization of 312-DCP with an increase of allyl absorbances, a decrease of swelling occurs, which means that the coagent participates more in crosslinking than in grafting and cyclization.
The working solution was prepared by taking 20 mL of the DPPH stock solution and diluting it with methanol to obtain the absorbance of about 0.97 ( 0.03) at 517 nm.
Method D is ratio subtraction spectrophotometry where ASC can be determined by dividing the spectrum of the mixture by the spectrum of the SAD (as a divisor) followed by subtracting the constant absorbance value of the plateau region then finally multiplying the obtained spectrum by the spectrum of the divisor.
A control sample with a high total bilirubin shows the typical reaction pattern with an early increase in absorbance readings after the addition of reagent 2.