Which physical quantity represents the rate of transfer of radiant energy or the energy emitted per unit time by a light source?

💡 Solution & Explanation

Radiant flux measures the total power emitted as electromagnetic radiation across all wavelengths per unit time, expressed in watts. Luminous flux evaluates radiant power weighted against the human eye's spectral sensitivity curve, measured in lumens. Illuminance quantifies luminous flux incident per unit surface area, measured in lux. Luminous intensity measures luminous flux emitted per unit solid angle in a specific direction, measured in candelas.