Radiometric dating is
Integral quantities (like radiant flux) describe the total effect of radiation of all wavelengths or frequencies, while spectral quantities (like spectral power) describe the effect of radiation of a single wavelength λ or frequency ν.
To each integral quantity there are corresponding spectral quantities, for example the radiant flux Φ.
The use of radiometers to determine the temperature of objects and gasses by measuring radiation flux is called pyrometry.
Handheld pyrometer devices are often marketed as infrared thermometers.
Radiometric dating (often called radioactive dating) is a way to find out how old something is.
The method compares the amount of a naturally occurring radioactive isotope and its decay products, in samples. It is the main way to learn the age of rocks and other geological features, including the age of the Earth itself.
Radiocarbon dating is one kind of radiometric dating, used for determining the age of organic remains that are less than 50,000 years old.
This helps to counter the effects of heating and squeezing, which a rock may experience in its long history.Spectroradiometry is the measurement of absolute radiometric quantities in narrow bands of wavelength. "Radiant emittance" is an old term for this quantity.Radiant flux emitted, reflected, transmitted or received by a surface, per unit solid angle per unit projected area. This is sometimes also confusingly called "intensity". This is sometimes also confusingly called "intensity".The amount of the isotope in the object is compared to the amount of the isotope's decay products.
The object's approximate age can then be figured out using the known rate of decay of the isotope.Radiometry is important in astronomy, especially radio astronomy, and plays a significant role in Earth remote sensing.