Heat energy transmitted from Lightbulbs

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Discussion Overview

The discussion centers on the differences in heat energy transmission and light production between incandescent bulbs and compact fluorescent lamps (CFLs). Participants explore the underlying mechanisms of light generation and the spectral characteristics of each type of bulb.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant notes that incandescent bulbs waste energy as heat and questions whether the difference lies in the radiated spectrums or the mechanics of light production.
  • Another participant explains that incandescent lights emit radiation across the visible spectrum and into the infrared, with light generation depending on temperature, typically around 2000-3000K.
  • A participant questions whether the light produced by CFLs can be accurately described as "white light," suggesting that their spectrum is actually narrow.
  • One participant agrees that CFLs produce white light by mixing red, green, and blue wavelengths, with the exact ratios varying based on gas mixtures and coatings used by manufacturers.

Areas of Agreement / Disagreement

Participants express some agreement on the differences in light production between incandescent bulbs and CFLs, but there is no consensus on the characterization of CFL light as "white light" due to its narrow spectrum.

Contextual Notes

Participants discuss the dependence of light output on temperature and manufacturing choices, but do not resolve the implications of these factors on energy efficiency or light quality.

johnl
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They say that incandescent bulbs waste a lot of energy in the form of heat, while cfl's do not. I want to understand why this is so. They both produce white light? Is it a difference in the radiated spectrums of each type of bulb, or does it have to do with the mechanics of making light by glowing the element in the incandescent vs light emission from the excited gas in the cfl? I don't know the answer, trying to figure it out.
 
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Incandescent lights produce radiation across the visible band and out into the infrared,
The amount of light they generate at each wavelength depends on the temperature - typically about 2000-3000K, so in this graph you can see that only a small amount of the light in in the visible band

e23_3.gif


CF produce only a few narrow wavelengths in the visible band, by balancing the amount of red, blue and green they produce it looks white.
 
So, would it be correct to say that the light produced by cfl's isn't actually "white light", in that the spectrum is actually narrow?
 
Correct - like a TV it makes white by mixing red/green/blue
The exact ratio depends on the gas mix and coatings on the bulb and so depends on the manufacturer -
you can design to either give an output like a regular bulb or a blue-er output that is closer to daylight.

spectra.jpg
 

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