Visible light is 'visible' because the energy of photons in this range of the spectrum corresponds to the excitation energy of pigment molecules, such as the vitamin A-based retinaldehyde chromophores bound to the protein opsin in the human visual system. Visible light has just the right amount of energy to elevate electrons between molecular orbitals and absorb light energy. The extended conjugated systems within pigments are essential in the absorbance qualities of these molecules. Lower energy light, such as infrared, does not elevate electrons between molecular orbitals in most chemical substances. Higher energy light, ultraviolet, can be destructive, often catalyzing chemical reactions.

The WikiPremed MCAT Course is a comprehensive course in the undergraduate level general sciences. Undergraduate level physics, chemistry, organic chemistry and biology are presented by this course as a unified whole within a spiraling curriculum. Please read our policies on Privacy and Shipping & Returns.  Contact Us. MCAT is a registered trademark of the Association of American Medical Colleges, which does not endorse the WikiPremed Course. WikiPremed offers the customers of our publications or our teaching services no guarantees regarding eventual performance on the MCAT.

Creative Commons License
WikiPremed is a trademark of Wisebridge Learning Systems LLC. The work of WikiPremed is published under a Creative Commons Attribution NonCommercial ShareAlike License. There are elements of work here, such as a subset of the images in the archive from WikiPedia, that originated as GNU General Public License works, so take care to follow the unique stipulations of that license in printed reproductions.