Transmittance
（重定向自Light transmittance）
![Diagram of Beer-Lambert Law of transmittance of a beam of light as it travels through a cuvette of width l.](/Images/godic/202501/24/Beer_lambert11358.png")
![Earth's atmospheric transmittance over 1 nautical mile sea level path (infrared region[1]). Because of the natural radiation of the hot atmosphere, the intensity of radiation is different from the transmitted part.](/Images/godic/202501/24/Atmospheric.transmittance.IR1358.jpg")
![Transmittance of ruby in optical and near-IR spectra. Note the two broad blue and green absorption bands and one narrow absorption band on the wavelength of 694 nm, which is the wavelength of the ruby laser.](/Images/godic/202501/24/Ruby_transmittance.svg1358.png")
Transmittance of the surface of a material is its effectiveness in transmitting radiant energy. It is the fraction of incident electromagnetic power that is transmitted through a sample, in contrast to the transmission coefficient, which is the ratio of the transmitted to incident electric field.