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About "Ask A Scientist!"

On September 17th, 1998 the Ithaca Journal ran its first "Ask A Scientist!" article in which Professor Neil Ashcroft , who was then the director of CCMR, answered the question "What is Jupiter made of?" Since then, we have received over 1,000 questions from students and adults from all over the world. Select questions are answered weekly and published in the Ithaca Journal and on our web site. "Ask A Scientist!" reaches more than 21,000 Central New York residents through the Ithaca Journal and countless others around the world throught the "Ask a Scientist!" web site.

Across disciplines and across the state, from Nobel Prize winning scientist David Lee to notable science education advocate Bill Nye, researchers and scientists have been called on to respond to these questions. For more than seven years, kids - and a few adults - have been submitting their queries to find out the answer to life's everyday questions.

Published: 10 December, 1998

How does a fluorescent light bulb work?

A fluorescent lamp consists of a glass tube that is filled with mercury vapor at low pressure. The inside of the tube is coated with a phosphorous substance. Two coiled metal (tungsten) filaments are at each end of the tube. When an electric current flows through the filaments they start to get hot and glow (like a regular light bulb). When we apply a voltage between the two filaments and electrons get sucked from one filament to the other. While zipping through the tube, electrons crash into mercury atoms, which start to glow and send out ultra-violet (UV) light.

UV-light is very, very violet. Actually it is so violet that you can't see it, but you can get a sunburn from it. So on its own UV-light wouldn't make a useful lamp: that's why there is a phosphorous substance in the inside of the glass tube. When UV-light hits the phosphor atoms, they absorb the UV light and send out the white light that illuminates your room. The conversion of light from one type to another is called fluorescence, which gave the fluorescent lamp its name.

Fluorescent lights conserve energy. For the same amount of light they need less power than usual light bulbs. By the way, the funny shaped light bulbs made of bent glass tubes in the supermarket are actually fluorescent lamps. Please don't play and break fluorescent lamps: they contain chemicals that are poisonous. When disposing of a fluorescent lamp, you should call the Recycling Center!

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