Light is a form of electromagnetic radiation. It comes in discrete packets called photons. Light also behaves as if it were propagated in waves. The amount of energy contained in a single photon is inversely proportional to its wavelength: the shorter the wavelength, the greater the energy of the photons. For example, a photon of red light of wavelength 660 nm has less energy than a photon of blue light at 430 nm.
Two things are required for photons to be active in a biological process:
► Photons must be absorbed by a receptive molecule.
► Photons must have sufficient energy to perform the chemical work required.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.