Questions about Light: Will Cold Chamber Affect Beam?

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Discussion Overview

The discussion revolves around the effects of a cold chamber on a light beam passing through lenses, particularly focusing on the energy of photons and the implications of the chamber's temperature and composition, specifically with carbon dioxide present. The scope includes theoretical considerations and potential applications related to light behavior in different environments.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions whether the light beam will retain its heat or consist of low-energy photons after passing through a cold chamber.
  • Another participant notes that "temperature" is a concept that applies to collections of particles and that the specific effects on light depend on the type of matter in the chamber, mentioning phosphors as an example that can absorb and re-emit photons.
  • A participant specifies that carbon dioxide will be present in the chamber and inquires about the necessary information to calculate the energy of the photons at a temperature of -78º C.
  • Another participant suggests that the temperature of CO2 may not significantly affect the heat of the beam unless the increased density at lower temperatures causes more scattering of light, and provides a formula relating photon energy to wavelength.
  • This participant also introduces the concept of a "heat mirror" that reflects infrared radiation while allowing visible light to pass, suggesting it may be relevant to the application.

Areas of Agreement / Disagreement

Participants express differing views on the impact of the cold chamber's temperature on the light beam's energy, with no consensus reached on the specific effects or calculations needed.

Contextual Notes

The discussion highlights the dependence on the specific properties of the matter in the chamber and the need for additional information to make accurate calculations regarding photon energy.

Who May Find This Useful

Individuals interested in optics, thermodynamics, or applications involving light behavior in varying environmental conditions may find this discussion relevant.

EEstudentNAU
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If light passes through a fresnel lens and then through another lens focusing it a bit so it is not as concentrated (but still somewhat), and passes through a cold chamber, will the beam at the end still be hot, or will it be a bunch of low energy photons?
 
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"Temperature" means nothing in empty space -- it's a number that describes the statistics of a bunch of particles considered together. If you pass the light through a "cold chamber," then you're passing the light through some kind of matter. That matter could do almost anything to it, and you haven't specified what kind of matter it is. Phosphors, for example, absorb high-energy photons and re-emit lower-energy photons.

- Warren
 
Carbon dioxide will be in the chamber. Is there a way to calculate the photons energy? Say the carbon dioxide is at -78º C. What other information do I need?
 
I wouldn't expect the CO2 temperature to have any useful effect on the heat of the beam unless you're expecting the increased density at cold temperatures will scatter the light more. The energy present in a beam of light radiation is the amount of photons times the energy per photon, which is inversely proportional to wavelength. Energy of a photon is h*c/lambda

I don't know what your application is, but you might look into a "heat mirror". These will reflect the invisible infrared radiation that comes off of many light sources, and pass only the visible stuff.
 

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