Radiance is the brightness or intensity of light that is emitted by a source. It is measured in watts per square meter per steradian (W/m^2/sr). The radiance of a light source is determined by its luminous flux (the total amount of light emitted) and the area of the source from which the light is emitted.

Radiance is an important concept in lighting design, as it determines how bright a light source will appear to an observer. For example, a light source with a high radiance will appear brighter than a light source with a low radiance, even if both sources have the same luminous flux.

Radiance is also used in radiometry and photometry to measure the intensity of other types of electromagnetic radiation, such as infrared and ultraviolet radiation.

Here are some examples of radiance in everyday life:

* The sun is the most radiant object in the sky, with a radiance of approximately 1.36 × 10^6 W/m^2/sr.

* A typical light bulb has a radiance of about 100 W/m^2/sr.

* A candle flame has a radiance of about 1 W/m^2/sr.

* A laser pointer has a radiance of about 10^6 W/m^2/sr.

Radiance is a fundamental property of light that has important applications in lighting design, radiometry, and photometry.