Photon Interval vs Areal Density for Changing Intensity

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Discussion Overview

The discussion revolves around the relationship between photon frequency, areal density, and intensity in the context of incandescent bulbs. Participants explore how changes in intensity affect the frequency of photon emissions and the density of photons emitted, considering both theoretical and practical implications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants suggest that reducing the intensity of an incandescent bulb affects both the frequency of photon emissions and the areal density of photons, but the extent of each decrease is questioned.
  • One participant claims that the intensity primarily increases or decreases the number of photons, while the energy of the photons is related to their frequency.
  • Another participant proposes that if the frequency of emission decreases, the areal density will also decrease proportionally.
  • Some participants argue that the relationship between flux and photon density implies that doubling the flux would double the rate at which photons pass through a given area, but this does not necessarily mean the areal density must change.
  • A participant discusses the nature of incandescent bulbs as black body sources, suggesting that the number of collisions (and thus emissions) is related to temperature, but questions remain about the constancy of areal density.
  • Planck's law is referenced, indicating that higher temperatures lead to increased radiation emission across wavelengths, which raises questions about the constancy of emission rates.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between photon frequency, areal density, and intensity. There is no consensus on how these quantities interact, and the discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Some statements rely on assumptions about the behavior of photons and the nature of black body radiation, which may not be universally accepted. The discussion includes references to specific physical laws and concepts that are not fully explored or agreed upon.

greswd
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When one reduces the intensity of let's say, an incandescent bulb (by varying the resistance, as seen in many homes), which decreases more, the photon frequency (not related to wavelength, but the time interval between photon emissions) or the areal density of the photons?

To what extent does each decrease?
 
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The emissions of photon related to the frequency.
 
The intensity just can increase or decrease the number of photons, but the movement enargy of photons related to the frequency of light
 
ceil said:
The intensity just can increase or decrease the number of photons, but the movement enargy of photons related to the frequency of light

I don't understand what you're saying.
 
can someone please help me
 
If the frequency of emission decreases the aerial density will do too. By the same proportion.
 
Jilang said:
If the frequency of emission decreases the aerial density will do too. By the same proportion.
thanks. do you have any literature on this?
 
No. It's just a consequence of flux. If you double the flux you double the rate of that the photons pass through a shell. Given that they all travel at c, the speed of light, the density in the shell must be double.
 
Jilang said:
No. It's just a consequence of flux. If you double the flux you double the rate of that the photons pass through a shell. Given that they all travel at c, the speed of light, the density in the shell must be double.
No, you can double the flux by halving the interval and leaving the density unchanged. The photons will still travel at c.

I want to know the density and interval relationship for an incandescent bulb, or any other type of light source you know of.
 
  • #10
greswd said:
When one reduces the intensity of let's say, an incandescent bulb (by varying the resistance, as seen in many homes), which decreases more, the photon frequency (not related to wavelength, but the time interval between photon emissions) or the areal density of the photons?

To what extent does each decrease?
Incandescent light bulbs emit light as a result of heat. We can treat the bulb as a black body source. The question you ask is really specific, I will answer according to my intuition however if I am mistaken feel free to correct.

A black body source emits light as a result of collisions between atoms and molecules in the atomic structure. As the material heats up, the atoms and molecules start to collide with higher kinetic energies, thus in a given time frame more collisions occur. We can roughly treat each collision as an emission of a single photon. Therefore the rate of collisions is the rate of photon emission.

By areal density, I am assuming you mean the number of photons per unit area perpendicular to the radial emission (photon's travel path). We can then say that the areal density of of photons is roughly the number of collisions happening per unit area. Then no matter the temperature of the material, the areal density will remain constant - since the number of atoms, thus the number of collisions is constant.

So, at low temperatures the emission rate decreases, but the number of photons per emission (if it makes sense) remains constant.
 
  • #11
Jilang said:
No. It's just a consequence of flux. If you double the flux you double the rate of that the photons pass through a shell. Given that they all travel at c, the speed of light, the density in the shell must be double.

@Jilang, according to Nosebgr, depending on the system's dynamics, the areal density can be constant.

Nosebgr said:
Incandescent light bulbs emit light as a result of heat. We can treat the bulb as a black body source. The question you ask is really specific, I will answer according to my intuition however if I am mistaken feel free to correct.

A black body source emits light as a result of collisions between atoms and molecules in the atomic structure. As the material heats up, the atoms and molecules start to collide with higher kinetic energies, thus in a given time frame more collisions occur. We can roughly treat each collision as an emission of a single photon. Therefore the rate of collisions is the rate of photon emission.

By areal density, I am assuming you mean the number of photons per unit area perpendicular to the radial emission (photon's travel path). We can then say that the areal density of of photons is roughly the number of collisions happening per unit area. Then no matter the temperature of the material, the areal density will remain constant - since the number of atoms, thus the number of collisions is constant.

So, at low temperatures the emission rate decreases, but the number of photons per emission (if it makes sense) remains constant.
 
  • #12
Planck' law says that the higher the temperature of the body the more radiation it emits at every wavelength. There is one photon for each emission. The rate of emission therefore cannot be constant.
 
  • #13
Jilang said:
The rate of emission therefore cannot be constant.

Nosebgr didn't say that it was constant.
 
  • #14
I read his penultimate paragraph to say that the number of collisions was constant and the number of emissions was constant. The final paragraph seemed to contradict this though. Perhaps he can clarify this.
 

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