##  [Optical Transmittance](/optical-transmittance) 

  ##  [Optical Transmittance](https://engineering.quantumdictionary.io/optical-transmittance-0) 

  

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**Engineering & Applied Technologies Dictionary**

 







 

 

 

 



 

 

 

 

Definition

The fraction (or percentage) of incident optical power at a specified wavelength or spectral band that emerges from a sample on the far side, typically expressed as T(λ)=P_transmitted(λ)/P_incident(λ); transmittance is wavelength‑ and direction‑dependent and may be reported as total, direct (specular) or diffuse transmittance.