Constant Light without a source?

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    Constant Light Source
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Discussion Overview

The discussion centers around the feasibility of creating a constant light source using a laser pointer and two highly reflective parabolas. Participants explore the theoretical implications of light reflection and persistence within a closed system, considering both practical and physical limitations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant proposes that shining a laser into two facing parabolas could create a constant light effect through continuous reflection, though acknowledges that the light would eventually fade out.
  • Another participant suggests that while theoretically possible, the light must diffract off the air, which diminishes the beam strength, and that no mirror is perfect, limiting the number of reflections.
  • A different viewpoint expresses skepticism about the possibility for visible light or shorter wavelengths due to atomic granularity in mirror materials causing scattering, and mentions heat loss as a concern for longer wavelengths.
  • One participant draws a parallel to ring-down spectroscopy, noting that the "residence time" of light in a cavity can be a sensitive measure of the contents within that cavity.
  • A later reply expresses appreciation for the concept of ring-down spectroscopy, indicating a newfound understanding of the topic.
  • Another participant reiterates the initial idea, emphasizing that visible light is only seen when it exits the mirror system.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of creating a constant light source, with some supporting the theoretical possibility while others highlight significant physical limitations. No consensus is reached regarding the practicality of the proposed setup.

Contextual Notes

Limitations include the assumptions about mirror perfection, the effects of diffraction and scattering, and the implications of heat loss in relation to different wavelengths of light.

Kazza
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Constant Light without a source?

Is it possible to create a constant light using a laser pointer and two highly reflective parabolas. If the two parabolas open out to face each other, and then you shine the laser into one, would the laser reflect until it reaches the centre and then continualy bouncing back and forth creating a constant light, at this point turning the laser off cause there to be no light source. Eventually this would fade out but is it possilbe.
Any ideas on where to buy products for this would be usefull.
 
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In theory, an idea such as this should be possible. However, in order for the light to be seen, it has to diffract off of the air, which obviously diminishes the beam strength. Also, since no mirror is perfect, even in a vacuum the beam would not continue to propagate infinitely.
 


I don't expect this to be possible for visible light, or EM radiation of wavelength shorter than microwave. Anything you make the mirrors out of will be composed of atoms, and so the granularity will have a deteriorating/dispersive effect on multiple reflections. There can be a few, or even a few hundred reflections, but very soon the light will scatter out of the apparatus. Unfortunately, for much longer wavelengths you have another problem: heat loss.
 


Andy Resnick said:
This sounds very similar to the principle of ring-down spectroscopy; the "residence time" of light in a cavity is a very sensitive measure of what is in the cavity.

http://en.wikipedia.org/wiki/Cavity_ring_down_spectroscopy

Wow, I didn't know there was such a thing. Thanks for opening my eyes.
Cheers
 


Kazza said:
Is it possible to create a constant light using a laser pointer and two highly reflective parabolas. If the two parabolas open out to face each other, and then you shine the laser into one, would the laser reflect until it reaches the centre and then continualy bouncing back and forth creating a constant light, at this point turning the laser off cause there to be no light source. Eventually this would fade out but is it possilbe.
Any ideas on where to buy products for this would be usefull.

Keep in mind that the only light you see is light that has left the system of mirrors.
 

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