Encyclopedia > letter R > radiant energy

Radiant Energy

Author: the photonics expert Dr. Rüdiger Paschotta (RP)

Definition: energy of some electromagnetic radiation which is emitted, transmitted or absorbed during some interval of time

Alternative term: optical energy

Categories: article belongs to category general optics general optics, article belongs to category light detection and characterization light detection and characterization, article belongs to category optical metrology optical metrology

Units: J

Formula symbol: <$Q_\textrm{e}$>

DOI: 10.61835/w3r Cite the article: BibTex plain text HTML Link to this page! LinkedIn

In radiometry, a radiant energy is the energy of some electromagnetic radiation which is emitted, transmitted or absorbed during some interval of time. The corresponding photometric quantity is the luminous energy <$Q_\textrm{v}$>. A final value of the radiant energy is obtained for light pulses, or for a considered limited time interval for continuous radiation.

The term radiant energy is common in fields like illumination and radiative heating (with infrared radiation), but less so in laser technology, where it is more common to use the term pulse energy for the energy in an optical pulse.

Many radiometric quantities are derived from the radiant energy. For example, the radiant flux is the radiant energy per unit time, which in optics corresponds to the optical power. A radiant exposure is the received radiant energy per unit area.

More to Learn

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Radiometry

Questions and Comments from Users

2024-01-10

Is radiant energy the same as photon energy? If radiant energy is the energy of electromagnetic radiation and the electromagnetic waves have photon energy, this seems to tell me that they are equivalent.

The author's answer:

Although radiant energy can be considered to be transported by photons, with the photon energy one usually means the energy of a single photon, rather than the energy e.g. of a light pulse.

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