Radiant Flux - Explanation and References

Radiant flux is the energy per unit time that is radiated from an optical source, expressed in terms of Watts. Light from any source flows through space, and so radiant flux is sometimes described as the time rate flow of radiant energy.

Radiant flux is also called radiant power. The symbol for denoting radiant flux is Φ.

In astronomical terms, the radiant power of stars is referred to as their luminosity. Radiant flux, or power, is the principle behind the working of a photographic flash meter.

The total amount of current, measured over a period of time, is directly proportional to the radiant energy that the light meter absorbs (for that period of time). The photographic flash meter measures the total amount of radiant energy received from the flash of the camera.

A radiant flux of 1W means that the source generates 1 J/s. The total energy produced by the source can be obtained by integrating the radiant flux over time.

References

• Photometry and Radiometry – Brown University
• Radiant Flux – Georgia State University
• Definitions of and relations between quantities used in radiation theory – Harvard