A lamp filament is made of tungsten. When made to glow, it emits a continuous spectrum-all the colors of the rainbow. When tungsten gas is made to glow, however, the light is a composite of very discrete colors. WHy is there a difference in spectra?
2007-05-31 13:56:49 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Physics
The filament is emitting blackbody radiation with a continuous spectrum based on its temp. It can emit pretty much any frequency because it has plenty of practically free electrons.
The gas can only emit and absorb light corresponding to its electronic resonances, so it has a discrete spectrum.
2007-05-31 14:02:25 · answer #1 · answered by Anonymous · 0⤊ 0⤋
A lamp filament is a macroscopic solid body made of many atoms closely packed together. The energy levels for the outer electrons of these atoms get closer because of the proximity of the tungsten atoms in the solid. Electronic transitions from one energy level to another (which result in light being emitted) could then have almost any energy values (i.e. from 0 eV to some limit I guess). It will looks like if it was continuous. That is, you will get a continuous spectrum of frequency in this case.
On the other hand a gas of tungsten atoms is a very different system. If the gas pressure is low you may even consider each atom as being isolated from each other. The electronic energy levels for the outer electrons are in this case quantized (or discrete). Light emitted by the electronic transition from one level to the other could only then be discrete being limited to a restricted set of energy levels.
2007-05-31 21:26:44 · answer #2 · answered by Anonymous · 0⤊ 0⤋
The gaseous spectrcum is discrete because it is caused by the de-excitation of electrons around the tungsten atoms, which have definite energies. The light from the lightbulb is the result of heat, therefore it follows the blackbody radiation laws, with a color dependent on temperature.
2007-05-31 21:01:58 · answer #3 · answered by supastremph 6 · 0⤊ 0⤋