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Re: Filament resistance, Color temperature



This discussion has raised in my mind the following question that has
occured to me before.

The surface of the Sun is about 5800 K and emits spectrum of light that
has a yellow cast. The filment of a light bulb, if made of tungsten,
could not be hotter than 3695 K, its melting point, and yet emits light
that appears white, even in the small clear bulbs used to demonstrate
series and parallel circuits. The white light should indicate that the
tungsten is at a higher temperature than the surface of the Sun. What am
I missing here?

Joe D. Darling


"Light bulb appears white" probably means that to your eye it appears
white. The eye however is easily fooled. Incandescent light has a
definite reddish cast relative to sunlight.

My "Physics Vade Mecum" Chromaticity diagram has a fluorescent lamp with an
equivalent temperature of 4800 K. I can't quickly find a color temperature
for incandescent.

Dr. Vern Lindberg 716-475-2546
Department of Physics Fax 475-5766
85 Lomb Memorial Drive
Rochester Institute of Technology
Rochester, NY 14623