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Scientific Glossary

Arc Lamp

An arc lamp is an optical source used in many kinds of instruments to provide high levels of brightness. Arc lamps are often filled with gases, such as krypton, mercury, or xenon. Developed in Germany during World War II for use in high-powered search lights, the particularly bright and penetrating xenon arc lamps are now used in both SPFs and IMAX theaters.
Assaying is the process of determining how much of a certain substance is present.


A cuvette is a small transparent tube (often rectangular) that holds a solution or a sample.

Diffraction gratings

Diffraction gratings are closely spaced, straight, parallel grooves on an aluminum surface which are able to separate (or diffract) white light into its component wavelengths. By the early 1950s they were rare but available, so Dr. Bowman was able to use one in his prototype SPF.


An electron is a negatively charged subatomic particle.


Fluorescence is the glow made by some materials when they are "excited by" (react to) light in the visible or invisible (ultraviolet) range. Molecules absorb photons (the smallest possible bits of light) at one wavelength of color and become excited. The molecules change slightly as they store the energy of the photons. As they change, they leak some of the energy to surrounding molecules. Using the remaining energy, the molecules emit new photons in different colors. This creates a fluorescent glow. (Click on film icon to watch an animation on the physics of fluorescence).

fluorescence animation 


A monochromator selects light from a narrow band of wavelengths using either a prism or a diffraction grating. High quality but very expensive monochromators were just beginning to be produced in the United States in the 1950s when Dr. Bowman used them in his instrument.


A chemical compound released by one neuron that acts as a messenger to another neuron.


The fluid ground substance of whole blood.

Ultraviolet (UV) light

Light radiation having wavelengths that places it outside the violet end of the visible spectrum, invisible to the human eye.

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