Light as an Ecological Factor1. Underlying principlesa. Electromagnetic radiation as a form of energyb. Energy emitted by objects such as the sun, earth, organisms, spans a spectrum of wavelengthsi. Amount of energy emitted is proportional to the fourth power of an object’s absolute temperature (Kelvin scale; Stefan-Boltzmann law)ii. The wavelength where maximum emission occurs is inversely proportional to the object’s temperature (Wien’s displacement law)c. Electromagnetic radiation has both wave and quantum (photon) propertiesd. The shorter the wavelength of radiation, the greater the amount of energy per photone. Portions of the electromagnetic spectrumi. Visible light / Photosynthetically active radiation (PAR): approx. 400-700 nanometers (nm)ii. Infrared radiation- Near infrared: approx. 700-5,000 nm- Far infrared: approx. 5,000 nm - 100,000 nmiii. Ultraviolet radiation- UV-A radiation: 320-400 nm- UV-B radiation: 280-320 nm- UV-C radiation: 200-280 nmf. Possible interactions of light and matter:
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Ultraviolet, Electromagnetic spectrum, b. Energy, iii. Ultraviolet radiation