irradiance

noun

1. (countable, uncountable)The act of irradiating; emission of rays of light.
2. (countable, uncountable)That which irradiates or is irradiated; lustre; splendour; brilliancy.
3. (countable, uncountable)The radiant power received by unit area of surface.

   “The geometry of the cone θ and the irradiance at the image of the carbon block were used to determine the absolute steradiancy of the energy in the cone θ as a radiometer calibration value.”