# Extinction/Absorption/Transmission spectra

1. Oct 19, 2009

### krindik

Hi,
This must be a text book question but I couldn't find exact definitions(quantitative) of these measurements
Extinction spectra:
Absorption spectra:
Transmission spectra:

eg.
Lets say electric field spectrum of some location/surface is calculated by illuminating a source with and without the presence of an object.
With the presence of the object = $E_{transmitted}(\omega)$
Without the presence of the object = $E_{incident}(\omega)$
Absorption spectra = $$\frac{E_{incident}(\omega) - E_{transmitted}(\omega)}{E_{incident}(\omega)}$$
Should it be $E$ or $E^2$ (energy) ?

Can somebody point me to a book/ web resource or the answers to these definitions?

2. Oct 19, 2009

### Andy Resnick

Usually the absorption, reflection, and transmission spectra are given in terms of the absorbed, reflected, or transmitted *energy* (intensity) sisnce that is what is measured. Also, the spectra are (usually) obtained by normalizing to the incident energy, to remove dependence on the source illumination.

3. Oct 19, 2009

### krindik

Could you give the exact definitions? Or any book?

4. Oct 19, 2009

### Born2bwire

Any engineering electromagnetics book will deal with the absorption, reflection and transmission of a wave. For example, Constantine Balanis' "Advanced Engineering Electromagnetics." Pretty much though, the coefficients are simply the ratio of the reflected or transmitted field with respect to the incident field. The energy coefficients are the square of the field coefficients if I recall correctly.