What is the definition of irradiance?

Irradiance is defined as the amount of power received per unit area, typically measured in watts per square meter (W/m²). This term is crucial in various fields, especially in physics and engineering, as it describes how much solar energy, or any other form of radiant energy, is received over a given surface area. Understanding irradiance is essential when evaluating the performance of solar panels, the heating of materials by light, and other applications involving light intensity.

The definition emphasizes the power aspect, which differentiates it from other related concepts. For instance, while total energy emitted by a light source refers to the cumulative amount of energy produced over time, irradiance focuses specifically on the power density impacting a particular surface at a specific moment. Similarly, speed of light and wavelength relate to the properties of light itself rather than the intensity perceived at a surface, making them distinct from irradiance, which is more about energy distribution over an area.