is the schoolboy's mnemonic for the colors of the spectrum (red orange, ...,indigo, violet) as seen, for example, in a rainbow after water drops have broken up "white" sunlight. Conversely, the different colors (wavelengths) of the light produced by a light source combine to give a "white" mix. It has always been assumed that the ideal mix is that of sunlight, and light sources have been carefully engineered to approximate the spectrum of sunlight as best possible.
But why go by the sun, why not by the human eye for which artificial light is meant? The light-sensitive cells in the retina respond to three prime colors¾a blue-violet, a pure green, and an orange-red. Westinghouse's lamp division in Bloomfield, N.J., has now developed a fluorescent light whose coating emits only these three colors for a mix of "white" light that makes meats look redder, fabrics more colorful, and gives most other things more pleasing colors. Sears Roebuck is now experimenting with these lights in some of its department stores.
But the new light not only makes dollars look greener, it also saves energy: The eye perceives the same brightness as with a conventional strip light when it uses only half the power.
Concerning our item on the Circlite (June 80), a reader has quite rightly taken us to task for mentioning only the efficiency of lights, i.e. the radiant output per input energy. The radiant energy that the eye cannot see (infrared and ultraviolet) is waste just like heat, and a better measure is the efficacy in lumens per watt, a lumen measuring the visible quantity of light. Although the efficiency of the incandescent lamp remains very low (8%), its efficacy has advanced an order of magnitude over the last 100 years: Edison's first carbon lamp ran at a little more than 1 lumen per watt; today's light bulbs achieve 15 to 20 1pw. However, a fluorescent lamp does increase the efficacy by a factor of five.
Circlite is a generic name, and it is not manufactured by Westinghouse only. There are also other designs enabling fluorescent lights to be screwed into conventional holders. The figure on the right shows the "SL" bulb now available in Europe, made by Philips of the Netherlands (known as Norelco in the US).
[More: "The electric lamp: 100 years of applied physics" by J.M. Anderson and J.S. Saby, Physics Today, Oct. 1979.]
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Vol. 8, No. 2
Newsletter: Access to Energy Newsletter Archive Volume: Volume 8 Issue/No.: Vol. 8, No. 2 Date: October 01, 1980 04:08 PM (For actual publication date see newsletter.) Title: Phase Three
Copyright © 2004 - Access to Energy Newsletter Archive
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