This range is known as the "visible light spectrum.

-quote-

"What we call "light" is actually several small packets of energy called "photons." A photon can carry different amounts of energy, which causes the photon to vibrate at a certain frequency. These photon frequencies range from billions of oscillation per second to less than one per second. This complete range of possible frequencies is known as the "electromagnetic spectrum.

Light enters the eye through a special lens in the cornea, which focuses the light onto a special area in the back of the eye called the retina. The surface of the retina contains a dense field of special cells that change shape when exposed to photons within a certain range of frequencies. This change in shape is translated into visual information by the optic nerve and sent to the portions of the brain which controls sight.

However, the retina's cells are only sensitive to a narrow range of photon frequencies. This range is known as the "visible light spectrum.

Light enters the lens of the camcorder and is focused onto the surface of a silicon-based chip known as a "Charge-Coupled Device (CCD)." A CCD consists of hundreds of microscopic sensors called "capacitors" underneath a layer of light-sensitive silicon. When photons within a certain frequency range strike the silicon, it excites the latter's electrons in such a way that a very small electrical charge is produced. In turn, the capacitors trap and store all these charges.

Next, a small computer reads each capacitor's stored charges, translates the charges into light intensity and uses this information to construct a two-dimensional map of the image projected onto the CCD. This image is then reproduced in the viewfinder screen for the human eye to see."

-end of quote-
Source(s):
http://www.ehow.com/how-does_5403161_sony-nightshot-works.html


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