Irradiance

Measure of radiant energy over surface area

In radiometry, irradiance is the radiant flux received by a surface per unit area. The SI unit of irradiance is the watt per square metre (symbol W⋅m−2 or W/m²). The CGS unit erg per square centimetre per second (erg⋅cm−2⋅s−1) is often used in astronomy.

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