UV Spectroscopy - Absorbance vs transmission

1. Jun 18, 2010

Moogie

Hi

In UV spectrscopy, is the definition of absorbance (A = ecl) derived from the definition of transmission (T = It/Io) where It is the transmitted light and Io is the incident light, or is the definition of transmission defined from absorbance.

Also A = -log(T) and T = 10^-A = 10-ecl.

It looks to me as though transmission is a physical quantity based on recorded data and then the definition of absorbance is based on this

thanks

2. Jun 19, 2010

Rajini

Hello,
In UV both transmission and absorption occurs..
You transmits the light and the sample absorbs the light..
May be you are familiar with Lambert-Beer law.

3. Jun 19, 2010

Andy Resnick

That's essentially correct; there is a slight difference in that absorbance can be expressed in terms that do not depend on the thickness of the sample (e.g. e*c, if I understand what you wrote).