What produces the photons in light bulb filament?

Click For Summary

Discussion Overview

The discussion centers around the mechanisms of photon production in light bulb filaments, particularly in incandescent bulbs. Participants explore the processes involved in thermionic emission, energy transitions in atoms, and the resulting electromagnetic radiation emitted by the filament.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that electrons emitted by thermionic emission from the filament may fall back and emit EM radiation as they decelerate into the filament.
  • Another participant provides an excerpt explaining that free electrons in the filament collide with atoms, causing vibrations that heat the atoms and lead to the emission of photons when electrons return to lower energy levels.
  • There is a question raised about why the emitted radiation is a continuum rather than discrete lines, prompting a discussion about energy levels in solids versus gases.
  • A participant proposes that in solids, energy levels form bands, resulting in a near-continuous spectrum (black body radiation), while gases produce discrete emission lines due to their characteristic energy levels.
  • A reference is made to a study that discusses the variation in emission spectra among different types of lamps, noting that incandescent lamps emit primarily like blackbodies.

Areas of Agreement / Disagreement

Participants express differing views on the nature of emitted radiation, with some supporting the idea of continuous spectra in solids and others noting the discrete lines in gases. The discussion remains unresolved regarding the specifics of photon production mechanisms in light bulb filaments.

Contextual Notes

Participants reference various sources and studies, indicating a range of perspectives on the topic. The discussion includes assumptions about energy levels and the conditions under which different types of lamps operate.

Barry Bonobo
Messages
6
Reaction score
0
What produces the photons in light bulb filament? I know that electrons are emmitted by thermionic emmission from the filament . . . do they then fall back into the filament and emit EM radiation as they de-accellerate into the filament?
 
Science news on Phys.org
Nice thanks. Here's the except with the explanation:

"As these free electron move through the filament at high speeds they are constantly bumping into the atoms that make up the filament, the impact energy vibrating and heating these atoms. Bounded electrons in the atoms of the filament are temporarily boosted to a higher energy level. When the electron returns to its original energy level they release the extra energy in the form of photons. Metal atoms release primarily infrared light photons which happen to be invisible to the human eye, but if heated to a high enough temperature (around 2,200 C) will emit the visible light seen from a bulb. "

I wonder now though why it's a nice continuum of EM radiation, rather than discrete lines of radiation we usually see. . .
 
I might be wrong but...

In a solid I believe the energy levels form bands rather than discrete levels. So you get a near continuous spectrum of radiation (Black body)

In a gas lamp the energy levels are discrete so you get characteristic emission lines.
 
http://www.asdi.com/getmedia/05be99...CTRAL-SIGNATURES-OF-NIGHTTIME-LIGHTS.pdf.aspx

Conclusion
We found substantial variation in the emission spectra of lighting types. Lamps that produce
light through heat (incandescent, quartz halogens, and fuel lamps) emit primarily like blackbodies, with
peak emission in the near infrared and emissions higher in the red than green and blue. Fluorescent,
metal halide, high pressure and low pressure sodium lamps are gas discharge lamps, which emit
different series of narrow emission lines. The identity of the gas discharge lamps can be discerned
based on the wavelength positions of the emission lines...

continues
 

Similar threads

  • · Replies 17 ·
Replies
17
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 72 ·
3
Replies
72
Views
7K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 16 ·
Replies
16
Views
5K
  • · Replies 15 ·
Replies
15
Views
5K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 10 ·
Replies
10
Views
23K
  • · Replies 6 ·
Replies
6
Views
10K
  • · Replies 9 ·
Replies
9
Views
4K