Knowledge that irradiance is the power per unit area incident on a surface.
Knowledge that irradiance is inversely proportional to the square of the distance from a point source.
Description of an experiment to verify the inverse square law for a point source of light.
Use of an appropriate relationship to solve problems involving irradiance, the power of radiation incident on a surface and the area of the surface.
Use of an appropriate relationship to solve problems involving irradiance and distance from a point source of light.