Is There Significant Energy Loss in Refracted and Focused Light?

[ssope]

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.

 

[Bob S]

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

 

[tiny-tim]

Hi Bob S!

And (I' m guessing ) is it (n₁-n₂)²/(n₁+n₂)² for general media?

 

[ssope]

Is there energy loss in light that is focused via a parabolic lens?

 

[tiny-tim]

Is there energy loss in light that is focused via a parabolic lens?

uhh? Bob S just said so … about 8%.

 

[Bob S]

I said 0% using a front-surface-silvered parabolic mirror, 8% through a refracting glass lens.
Bob S

 

[ssope]

I'm not sure that 0% is correct. I know that even the best silvered dielectric mirros offer 99% reflection