What is a candela?
A candela is a unit of measure indicating the luminous intensity (candlepower) of a light source in a specific direction; any given light source will have many different intensities, depending upon the direction considered. Why should I be concerned about the mercury content of lamps? Mercury is a highly persistent and toxic chemical that is building up to dangerous concentrations in fish, wildlife, and human beings throughout the US. By choosing high-efficiency lamps that contain less mercury, you help reduce the environmental impacts and health risks of lamp breakage during use, transport, and disposal. What is the proper disposal of fluorescent light bulbs? See www.lamprecycle.
A candela is a measurement of the intensity of light, used in the International Standard (SI) measurement system. In the modern age, it is technically defined as the intensity in a given direction of a source that emits monochromatic radiation of a frequency of 540 x 10^12 hertz and which has a radiant intensity in the same direction of 1/683 watts per steradian. The candela as a unit of measurement grew out of the desire to adopt a standard method to measure light. In the 19th century, each country had its own measure of light, most extremely difficult to reproduce with accuracy. At the beginning of the 20th century, groups of nations began adopting new standards, such as the international candle, which were based on a single type of lamp and much more consistent. Eventually, in the 1930s, it was decided that a more precise definition was needed. Initially, the candela was defined as the luminous emission of a Planckian radiator, a type of blackbody, at the temperature of freezing pla
