How can a mirror reflect 99,999% of incident light?

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Discussion Overview

The discussion revolves around the mechanisms by which mirrors, particularly those used in laser cavities, can reflect a high percentage of incident light, specifically 99.999%. Participants explore the properties of laser mirrors, the directional nature of photons, and the limitations of conventional mirrors across different wavelengths.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions how mirrors can achieve such high reflectivity and seeks a convincing explanation.
  • Another participant explains that laser mirrors are typically dielectric multilayer mirrors, which can reflect up to 99.99% in a specific wavelength range, while conventional metal mirrors like gold can reflect around 99.0% at certain wavelengths.
  • A participant emphasizes that no mirror can reflect all wavelengths at 99.999% efficiency and notes that regular mirrors have varying reflectivity across different wavelengths, particularly in the UV range.
  • It is mentioned that mirrors in laser cavities are specifically selected for high reflectivity in narrow wavelength ranges, indicating a finely tuned design.
  • A follow-up question is posed regarding the properties of a photon that contribute to its higher probability of detection in a narrow angle cone after reflection.
  • Another participant expresses reluctance to engage further due to perceived vagueness in the original question.

Areas of Agreement / Disagreement

Participants express differing views on the effectiveness of mirrors across various wavelengths and the specificity of laser mirrors. The discussion does not reach a consensus, particularly regarding the original question's clarity and the nature of photon behavior upon reflection.

Contextual Notes

The discussion highlights limitations in understanding the reflectivity of mirrors across different wavelengths and the assumptions regarding the properties of photons in relation to their detection angles.

intervoxel
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How can a mirror reflect 99,999% of incident light? Or in other words what makes a photon exiting a laser cavity so directional?
In fact, I never found a really convincing answer. Thank you.
 
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Laser mirrors are usually dielectric multilayer mirrors and commonly reflect up to 99.99% in target line. Also, even conventional metal mirrors have higher reflection coefficients in middle infrared range. For example, gold mirrors are 99.0% reflective at 10um wavelength.
 
intervoxel said:
How can a mirror reflect 99,999% of incident light? Or in other words what makes a photon exiting a laser cavity so directional?
In fact, I never found a really convincing answer. Thank you.

Your question is vague. No mirror can reflect ALL wavelengths at 99.999% efficiency. The regular mirror that you and I are used to may appear to be a good reflector of visible light, but put that in a UV-VIS spectrometer, and you'd be surprised at reflectivity spectrum, even in the visible range. And forget about UV, because such a mirror is hopeless.

Mirrors in laser cavity has been specifically selected so that it has the highest reflectivity in a very narrow range of wavelengths. So it has been finely tuned to work under a very narrow parameter.

Zz.
 
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ZapperZ said:
Your question is vague. No mirror can reflect ALL wavelengths at 99.999% efficiency. The regular mirror that you and I are used to may appear to be a good reflector of visible light, but put that in a UV-VIS spectrometer, and you'd be surprised at reflectivity spectrum, even in the visible range. And forget about UV, because such a mirror is hopeless.

Mirrors in laser cavity has been specifically selected so that it has the highest reflectivity in a very narrow range of wavelengths. So it has been finely tuned to work under a very narrow parameter.

Zz.
Nice answer, ZapperZ. Let's suppose now one single photon with the correct wave length to get maximum reflection. What happens to the properties of the photon to have higher probability of detection in a very closed angle cone in the direction of reflection?
 
intervoxel said:
Nice answer, ZapperZ. Let's suppose now one single photon with the correct wave length to get maximum reflection. What happens to the properties of the photon to have higher probability of detection in a very closed angle cone in the direction of reflection?

Why should I do this work for you especially when this is still quite vague?

Zz.
 
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The OP has received a warning for insulting another member. Thread closed.
 

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