Contrasting metal Vapor Lamps and a light Globe?

[rowshan]

How does a metal vapor lamp emit light?
How is it different to how a light globe does it?
Why does the vapor lamp only emit discrete wavelengths of light(in terms of quantised energy level model of the atom) ?
Are these incoherent?
Why does a candle emit all wavelengths of light(in terms of thermal motion of electrons)?

[Mao]

in a metal vapour lamp, electrons in the metal atom can absorb distinct energy levels that match the difference in energy between electron shells (subshells). only photons of specific frequencies can be absorbed, and only these frequencies can be emitted. A line spectra is obtained.

A light globe does so via thermal motion (varying degrees of vibration of electrons), emitting a range of frequencies.

In both cases, the light emitted is incoherent, as there are several (or a range of) frequencies, and even the same wavelengths are not necessarily in phase.

A candle emits light similar to a light globe, where the heat (from combustion) make the electron accelerate/vibrate, and a range of frequencies is emitted.

[rowshan]

On light globes:
"they use electrical current passing through a tungsten filament. As the atom heats up, they collide with each other. The electrons within the atom get raised into higher energy level. When they drop back to lower energy levels they emit light"
Are thermal vibrations also collisions?
I quote the A+ study guide. Are the incorrect?

[Mao]

=S don't think these are right. that would give rise to a line spectra.

I believe its more the valence electrons within the filament which vibrates, thus thermal motion of electrons.

[rowshan]

When the bulb is hooked up to a power supply, an electric current flows from one contact to the other, through the wires and the filament. Electric current in a solid conductor is the mass movement of free electrons (electrons that are not tightly bound to an atom) from a negatively charged area to a positively charged area.

As the electrons zip along through the filament, they are constantly bumping into the atoms that make up the filament. The energy of each impact vibrates an atom -- in other words, the current heats the atoms up.

Bound electrons in the vibrating atoms may be boosted temporarily to a higher energy level. When they fall back to their normal levels, the electrons release the extra energy in the form of photons. Metal atoms release mostly infrared light photons, which are invisible to the human eye. But if they are heated to a high enough level -- around 4,000 degrees Fahrenheit (2,200 degrees C) in the case of a light bulb -- they will emit a good deal of visible light.

From how stuff works.

Line spectra? You mean like discrete lines on those black coloured things. Isn't it possible for the light bulb to emit may frequencies(i think thats what it does any way).

To the problems still remains. Whats the difference between the two?

[mark_alec]

Though it is above what is required for you to know in VCE physics, if you read http://en.wikipedia.org/wiki/Black_body you might get some understanding for the light produced by a bulb (it can be modelled as a black-body.)