Is There Significant Energy Loss in Refracted and Focused Light?

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Discussion Overview

The discussion revolves around the energy loss in light when it is refracted through different media and when it is focused using parabolic lenses. Participants explore the extent of energy loss in these scenarios, considering both refractive media and reflective surfaces.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether there is significant energy loss (greater than 2%) in light refracted through media and focused via a parabolic lens.
  • Another participant calculates a power loss of approximately 4% for glass with an index of refraction of 1.5 when light is incident from air, leading to an estimated total loss of about 8% for a glass lens without anti-reflection coating.
  • A participant suggests a formula for calculating power loss in general media, seeking confirmation from others.
  • There is a claim that energy loss through a front-surface parabolic mirror is near zero, contrasting with the losses associated with glass lenses.
  • Another participant challenges the assertion of 0% loss, noting that even high-quality silvered mirrors typically reflect around 99% of incident light.

Areas of Agreement / Disagreement

Participants express differing views on the extent of energy loss in focused light, particularly between refractive and reflective surfaces. There is no consensus on the accuracy of the 0% loss claim for parabolic mirrors, as some participants question its validity.

Contextual Notes

Participants reference specific indices of refraction and power loss calculations, but there may be missing assumptions regarding the conditions under which these values apply. The discussion does not resolve the mathematical details or the applicability of the proposed formulas.

ssope
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I am wondering if there is a significant loss in energy (greater than 2%) in light that is refracted through media. I also am wondering the same about energy loss in light that is focused via a parabolic lens.
 
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Normally incident light on a refracting media with index of refraction n from air with n=1, or from the same media to air, has a power loss of

Power loss = (n-1)2/(n+1)2= 0.25/6.25 = 4% for glass with n=1.5.

So for going through a glass lens without anti-reflection coating, the loss is about 8%. The loss in a front-surface parabolic mirror is near zero.

Bob S
 
Hi Bob S! :smile:

And (I' m guessing :blushing:) is it (n1-n2)2/(n1+n2)2 for general media?
 
Is there energy loss in light that is focused via a parabolic lens?
 
ssope said:
Is there energy loss in light that is focused via a parabolic lens?

uhh? Bob S :smile: just said so … about 8%.
 
I said 0% using a front-surface-silvered parabolic mirror, 8% through a refracting glass lens.
Bob S
 
I'm not sure that 0% is correct. I know that even the best silvered dielectric mirros offer 99% reflection
 

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