Radiometry is the science of measurement of electromagnetic radiation and its application in physics, astronomy and geophysics. It is related to the photometry and represents the extension of this " measurement of light" in the areas of infrared and ultraviolet, but also the gamma rays dar.


The quantitative measurement of intensities of radiation is carried out with different types of detectors. Convert a portion of the radiation to heat or an electric signal, from which can be concluded, among other things on the nature of the radiating surface and the temperature. As a comparison often used to theoretically ideal " black body " and relevant for this radiation laws.

Radiometric quantities

In order to describe the properties of the radiation source, receiver and irradiated materials, one has defined five radiometric quantities. You meet five photometric quantities that due to the limited wavelength interval of visible light - spectrally weighted her special case - the standard CIE photopic curve.

The radiation flux density (also irradiance ) is defined as the radiant flux or luminous flux which crosses the surface element. The radiant energy per unit of time which is incident on an area element is referred to as irradiance, physiologically weighted as illumination.

The radiation energy emitted per unit time from a surface element, is called emittance, physiologically weighted as radiance.

The radiation density (also radiance ) is the total radiance of the radiation energy through a surface element in a given direction per unit of time is in a Raumwinkelement, or coming from the latter. Weighted Physiologically speaking of the luminance that specifies the brightness perception. is the seemingly luminous surface.


The detectors for the physical measurement of radiation quantities are called radiometers. Of the above-mentioned five sizes amount of radiation, irradiance and radiance to be measured mainly.

A radiometer consists of the input optics ( or the measuring aperture / antenna), the spectral filter, the actual sensor, associated electronics and the display device or display.

Gamma radiometry

The radiometry of gamma radiation in geophysics and other geosciences an important method for the determination of rocks and their fiber content. It is based on the radioactivity of the isotopes contained in them, so its spontaneous transformation into other chemical elements. The resulting decay processes in high-energy gamma radiation has a typical energy distribution, the so-called gamma spectrum for each isotope. The quantitative analysis of the natural isotopes ( particularly uranium, thorium, potassium-40, and carbon -14) allows to characterize the rock.