Efficacy of light.

Discussion in 'Physics' started by PRS, May 21, 2011.

  1. PRS

    Thread Starter Well-Known Member

    Aug 24, 2008

    Here is an excellent source on the topic, courtesy beenthere.

    As I said on another thread I had two experiences with trying to use 277 volt florescents at 240 volts where the light was very poor. This is only a 13% drop in power and the unwise would probably meant this was only a 13% drop in luminosity. But no, the drop in luminosity was greater than 50 percent as far as I could tell. This puzzled me and still does even after reading the wiki article above. That article explained luminous flux and the eye's ability to see only certain wavelengths of life to be the culprit. Or did I miss something?

    I recently bought a package of florescent bulbs purporting to give out the same amount of light as 100 watt incandescents, but using only 23 watts of power. Does anyone know just what it is that makes this happen? Perhaps I missed something in that article.
  2. BillO

    Distinguished Member

    Nov 24, 2008
    The ballast circuit that fluorescent light need to operate does not tolerate large input voltage changes. A relatively small variance will greatly affect their performance.

    The method fluorescent lights use to produce light from electricity is hugely different than the way an incandescent bulb works, and is far more efficient. Incandescent bulbs work by heating up an tungsten wire until it glows white hot. Most of the energy goes into heat.

    Fluorescent lights use high-voltages to excite mercury vapor which produces UV light that then causes a phosphor coating on the inside of the glass tube to fluoresce which produces the visible visible light.