radiometriin

Radiometry is the science of measuring electromagnetic radiation, focusing on the absolute physical energy of light and other forms of radiation regardless of how the human eye perceives it. It defines quantities that describe the power and distribution of radiant energy as a function of location, direction, and wavelength. Core radiometric quantities include radiant flux (power), radiant intensity, irradiance, radiance, and radiant exitance, as well as spectral power distributions that specify how energy is distributed across wavelengths.

Radiometry is distinct from photometry. Photometric measurements relate to human vision and use luminous quantities tied to the eye’s sensitivity, such as luminous flux, illuminance, and luminance. Radiometric measurements use energy-based units and functions that are wavelength dependent, such as watts (W), watts per steradian (W/sr), watts per square meter (W/m^2), and spectral radiance units like W/(m^2 sr nm). Measurements can be broadband or spectrally resolved.

Instruments used in radiometry include radiometers for measuring radiant energy, spectroradiometers for detailed spectral power distributions, radiometric cameras, bolometers, and photodiode-based detectors. Pyrometers are specialized devices for high-temperature radiance. Calibration relies on traceable standards such as blackbody sources and integrating spheres to ensure accuracy across conditions and wavelengths.

Applications span remote sensing, astronomy, solar energy and photovoltaics, environmental monitoring, materials testing, lighting design, and radiative heat transfer analysis. Radiometry provides fundamental data for calibrating sensors, evaluating light sources, modeling energy exchange, and supporting scientific and engineering decisions that depend on precise energy measurements across the electromagnetic spectrum.