Mirror box with 1 candela of luminous intensity light source

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Discussion Overview

The discussion revolves around the properties and implications of a mirror box containing a light source with 1 candela of luminous intensity, specifically focusing on the reflection of light within the box and the appropriate measurements of light intensity and energy. The scope includes theoretical considerations, measurement units, and potential resonant behaviors of the system.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants note that a simple mirror can reflect 99.9% of visible light, raising questions about the implications for light intensity within the box.
  • Others emphasize the importance of considering the shape of the box and the light source when making measurements.
  • There is a discussion about the appropriateness of using "candela" as a unit of measurement, with some arguing it is not suitable for quantifying the total light in the box.
  • One participant suggests that the box could be modeled similarly to a transmission line, where the geometry affects the number of reflections and energy buildup.
  • Another participant proposes that if the box is resonant at the frequency of the light source, it could lead to significant energy storage, while non-resonance would complicate energy input.
  • Some participants question whether it is possible to measure total lumens from the inner walls of the box, given the high reflection rate.
  • There are mentions of the concept of Q factor and how it relates to energy density and power loss in the system.
  • Concerns are raised about the measurement of luminous intensity within a reflective cavity and whether it makes sense to quantify intensity in this context.

Areas of Agreement / Disagreement

Participants express differing views on the appropriateness of using candela as a measurement unit and the implications of the box's geometry on light behavior. There is no consensus on how to accurately measure or characterize the light within the box, indicating ongoing debate and exploration of the topic.

Contextual Notes

Participants highlight limitations in the discussion, such as the lack of specified geometry for the box and the complexity of measuring light intensity versus energy within a reflective cavity. The assumptions about resonance and the behavior of light in the box remain unresolved.

  • #61
As has been said several times the answer depends upon the details. State a specific question: shape size material wavelength. Specific. This is physics not a debating society
 
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  • #62
it would be RF broadband 50MHz - 900MHz
in a 3m cuboid, 0.5 metal aluminium walls
 
  • #63
How is it fed? The wavelength then is .3 m to 6m. This is a waveguide problem and will change drastically over this band of frequencies. It may be very complicated. What precisely do you want to know?
 
  • #64
a 3m waveguide can do up to the 6m λ, so it will reflect all the frequencies concerned .
on an receiving antenna, that a 1W RF transmitter source might induce 1mW. But inside a RF reflective (metal) enclosure, this same scenario might induce more than the 1mW on a receiving antenna because of the duplication of apparent radiation sources of the reflections? maybe it might induce near 1W?
 
  • #65
It might. Of course it might not. Its complicated. See previous. I'm done.
 
  • #66
I am amazed at the number of attempted answers - why?
The question is flawed and can't be answered. As has been pointed out, candela are a measure of luminous intensity. More specifically, 1 candela = 1 lumen/ steradian.

The OP did not specify the solid angle over which the light source has a luminous intensity of 1 candela. A laser might emit over a solid angle of 1E-6 steradian, a uniform point source that emitted over all angles would emit over 4 pi steradians.

So in terms of luminous flux you could have anywhere from about 1E-6 to 12.566 lumens.

The real problem is that candela is a measure for a light source. You have a sealed box that doesn't let light out, so by definition it can't be a light source.

From the information the OP provided you can't even determine how many lumens are inside the box, so asking about luminous intensity is non-sensical. Ask a better question if you want an answer. Better yet, do a search on "integrating sphere equation." At least that would tell you how to ask the question (hint you have to specify the flux of the source). More importantly it would let you calculate the answer.

BTW: since lumens are a psychophysical unit you couldn't even determine the radiant energy inside the box.
 
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  • #68
Eric Bretschneider said:
I am amazed at the number of attempted answers - why?

People are trying to help. So far the OP wants to know how many candelas or maybe watts or maybe joules there are in an unspecified system involving light or maybe microwaves. People are guessing, but is it really any wonder we haven't guessed right yet? The OP is unhappy that the "wiz kids" haven't answered his question, but we're not mind readers. (Some of us, however, are very good guessers)

The OP is also starting multiple related theads - three or maybe four - asking similar questions. It's pretty clear he has a question in mind, but he doesn't want to come right out and ask it. It likely involves microwaves, but he's asking about light. I'm not sure why he thinks this secrecy and dancing around the real question will be helpful.
 
  • #69
Eric Bretschneider said:
Better yet, do a search on "integrating sphere equation."
Yes. This will likely be wildly inaccurate for the situation described but it is definitive and provides "scientific formula" which seems to be sufficient to the OP. In fact the following does a lovely job on the integrating sphere:

https://www.labsphere.com/site/assets/files/2551/integrating_sphere_theory_apps_tech_guide.pdf

.
 
  • #70
Vanadium 50 said:
People are trying to help. So far the OP wants to know how many candelas or maybe watts or maybe joules there are in an unspecified system involving light or maybe microwaves. People are guessing, but is it really any wonder we haven't guessed right yet? The OP is unhappy that the "wiz kids" haven't answered his question, but we're not mind readers. (Some of us, however, are very good guessers)

The OP is also starting multiple related theads - three or maybe four - asking similar questions. It's pretty clear he has a question in mind, but he doesn't want to come right out and ask it. It likely involves microwaves, but he's asking about light. I'm not sure why he thinks this secrecy and dancing around the real question will be helpful.
sorry new at this forum thing, the decorum is unfamiliar but this is more accurately what I'm trying to ask
 
  • #71
hutchphd said:
Yes. This will likely be wildly inaccurate for the situation described but it is definitive and provides "scientific formula" which seems to be sufficient to the OP. In fact the following does a lovely job on the integrating sphere:

https://www.labsphere.com/site/assets/files/2551/integrating_sphere_theory_apps_tech_guide.pdf

.
thank you, it is too advanced for me. but this is more accurately what I'm trying to ask
 
  • #72
i found the answer it is called an

"Integrating sphere"​

 

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