defr Glossar

Transmittance, spectral τ(λ)

Ratio of the transmitted spectral radiant flux Φout λ) to the incident spectral radiant flux Φin λ).

$\tau \left( \lambda \right) = \frac{\phi_{\text{out}} \left( \lambda \right) }{\phi_{\text{in}} \left( \lambda \right)}$

Spectral transmission
Fig. 50: Spectral transmission

In many cases, the transmittance is displayed by photometers in addition to the absorbance (formerly called extinction).


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