Transmittance





In optics and spectroscopy, transmittance is the fraction of incident light at a specified wavelength that passes through a sample.


 * $$\mathcal{T} = {I\over I_{0}}$$

where $$I_0$$ is the intensity of the incident light and I is the intensity of the light coming out of the sample. The transmittance of a sample is sometimes given as a percentage.

Transmittance is related to absorbance A as
 * $$A = - \log_{10}\mathcal{T}\ = - \log_{10}\left({I\over I_{0}}\right)$$

or, using the natural logarithm
 * $$A = - \ln\mathcal{T}\ = - \ln\left({I\over I_{0}}\right)$$

From the above equation and the Beer-Lambert law, the transmittance is thus given by


 * $$\mathcal{T} = e^{-\alpha \, x}$$,

where $$\alpha$$ is the attenuation coefficient and $$x$$ is the path length. Note that the term "transmission" refers to the physical process of light passing through a sample, whereas transmittance refers to the mathematical quantity.

Transmitance Transmission (Physik) Transmitancia Transmittance Trasmittanza Transmissão (física)