Radiometry and Photometry: Two Visions of One Phenomenon
Radiometry, the measurement of the energy of electromagnetic waves (EMW) is one of the most important fields of experimental physics, reaching all Natural Sciences. Photobiology, for instance, is based in the quantification of the action of light on biological systems. The interaction of EMW with photosensitive cells (an eye in a mammalian, for instance) is key in the understanding of the interaction of living beings with their environment. A human eye is sensitive only to a fraction of the EM spectrum, ranging approximately from 400 to 760 nm. Eye’s sensitivity varies with wavelength, growing from 400 to 555 nm, where it reaches a maximum, then monotonically decreasing up to 760 nm, where it reaches a value of zero. That is the reason of the existence of two different (though related) system of units. In one hand the radiometric or energetic units, characterizing the energy of a light beam and, on the other, the photometric units, characterizing the action of EMW upon a human eye. Both systems are often confused, and the extent and exact definition of their magnitudes misinterpreted, without a precise relation among related units of both systems. This is so even in some textbooks. In the present contribution we will try to clarify all these topics. This paper could be useful in courses of Optics, Ophthalmic Optics, Metrology and design of illuminating systems.
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
This work is licensed under the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) license.