Fresnel Lens and Parabolic Reflectors | Hacker News Reader

Fresnel Lens and Parabolic Reflectors

parabolixlight.com

21 pointstontonius15 comments

The behavior of light between materials is very interesting. In the below Fermilab video "Why does light bend when it enters glass?" several theories are explained which helped me understand the principals involved.

https://www.youtube.com/watch?v=NLmpNM0sgYk

Can anyone suggest a good explainer on light reflection at a similar level to the Fermilab ones?

Search for "how does refraction work" in YouTube?

My experience with fresnel lenses growing up was with the sheet magnifiers my grandmother would use to read; I could melt asphalt with them and it acted like my own laser beam. I always wanted to make one of these solar cooking apparatus stands but it was ... frowned upon ... by my parents: https://www.bealsscience.com/post/2016/10/04/solar-death-ray...

What's a flattened version of the parabolic reflector look like?

I think you're basically describing a concentrated solar plant, for example that giant array of mirrors on the way to Vegas (Ivanpah).

Ah yes, the one that cooks birds in flight.

Not quite the same thing, but the large mirror arrays used in those giant solar power plants are analogous, though without the circular symmetry of a Fresnel lens. An issue is efficiency: Each groove shadows its neighbor.

In fact there's no reason why a Fresnel lens can't be made from rectangular panels instead of circular grooves, except that the latter are easy to cut on a lathe.

The reflexive honeycomb used ubiquitously in automotive contexts is exactly that.

Plane

Plain

All of the light ray diagrams in the article are incorrect.

Can you please elaborate? I couldn't figure out what was incorrect in them

Not sure which aspect the earlier post meant but the rays are only refracting on the exit surface, when of course they also refract on the entry surface.

That’s it.

the world of lenses have fascinated me since I learned about it after having to research why VR is blurry outside the sweetspot.

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