*Attention:* The IES website will be temporarily unavailable from May 9th to May 13th for site updates. We apologize for any inconvenience and will provide an update closer to the time. Thank you for your continued support of the Illuminating Engineering Society.
DonateJoinMy IES

absorptance, α

[7.6.1] α = Φa/Φi

The ratio of the absorbed flux to the incident flux.

Note: The sum of the hemispherical reflectance, the hemispherical transmittance, and the absorptance is 1.0.

« Back to Definitions Index