The watt per steradian (W/sr) is a unit of power density in the International System of Units (SI). It is used to measure the intensity of radiation emitted by a point source in a particular direction.

The unit is derived from the watt, the SI unit of power, and the steradian, the SI unit of solid angle. One watt is equal to one joule per second. One steradian is equal to the solid angle subtended by a sphere at its center.

The watt per steradian is a small unit of power density. For example, the sun emits about 389 W/sr in the visible spectrum. What is the unit of radiant intensity? Radiant intensity is a measure of the power of light emitted by a particular source in a particular direction. It is typically measured in units of watts per steradian (W/sr). Is radiance the same as intensity? No, radiance is not the same as intensity. Intensity is a measure of the amount of power per unit area, whereas radiance is a measure of the amount of power per unit area per unit solid angle. Is radiant flux same as intensity? No, radiant flux is not the same as intensity. Radiant flux is a measure of the total amount of energy emitted by a light source, while intensity is a measure of the amount of energy emitted per unit area.

#### What is the formula of radiant power?

Radiant power is the rate at which energy is emitted, transported, and absorbed by a surface per unit area. It is a measure of the intensity of electromagnetic radiation and is most commonly expressed in units of watts per square meter (W/m2). Radiant power can also be expressed in terms of joules per second (J/s) or calories per second (cal/s).

##### What is irradiance vs radiance?

Radiance is the power of electromagnetic radiation per unit area per unit solid angle, in units of watts per square metre per steradian (W·m^−2·sr^−1). It is a measure of the intensity of electromagnetic radiation.

Irradiance is the power of electromagnetic radiation per unit area, in units of watts per square metre (W/m^2). It is a measure of the intensity of electromagnetic radiation.