What is transmittance?

  • (noun): The fraction of radiant energy that passes through a substance.
    Synonyms: transmission

Transmittance

In optics and spectroscopy, transmittance is the fraction of incident light (or other electromagnetic radiation) at a specified wavelength that passes through a sample. A related term is absorptance, or absorption factor, which is the fraction of radiation absorbed by a sample at a specified wavelength. Occasionally one also hears the terms visible transmittance (VT) and visible absorptance (VA), which are the respective fractions for the spectrum of light visible radiation. In equation form,

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Some articles on transmittance:

Standards For Sunglasses
... The five ratings for transmittance (filter) under this standard are based on the amount of absorbed light, 0 to 4, with "0" providing some protection from UV radiation and ... The European standard EN 18362005 has four transmittance ratings "0" for insufficient UV protection, "2" for sufficient UHV protection, "6" for good UHV ... There is no rating for transmittance protection for radiation of up to 400 nm ("UV400"), as required in other countries (incl ...
Measuring Thermal Transmittance
... Whilst calculation of thermal transmittance can readily be carried out with the help of software which is compliant with ISO 6946, a thermal transmittance calculation does not fully take ... into account it is necessary to carry out a thermal transmittance measurement ... ISO 9869 describes how to measure the thermal transmittance of a roof or a wall by using heat flux meters ...
Thermal Conductivity - Definitions - Transmittance
... A third term, thermal transmittance, incorporates the thermal conductance of a structure along with heat transfer due to convection and radiation ...
Transmittance
... In optics and spectroscopy, transmittance is the fraction of incident light (or other electromagnetic radiation) at a specified wavelength that passes through a sample ... Occasionally one also hears the terms visible transmittance (VT) and visible absorptance (VA), which are the respective fractions for the spectrum of light visible radiation ... radiation and I is the intensity of the radiation coming out of the sample and and are transmittance and absorptance respectively ...
Thermal Transmittance
... Thermal transmittance, also known as U-value, is the rate of transfer of heat (in watts) through one square metre of a structure divided by the difference in temperature across the structure ... parts of a building have a low thermal transmittance whereas poorly insulated parts of a building have a high thermal transmittance ... A × U × (T1 - T2) where Φ is the heat transfer in watts, U is the thermal transmittance, T1 is the temperature on one side of the structure, T2 is the temperature on the other side of the ...