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[-] Redjard@lemmy.dbzer0.com 8 points 10 months ago

There is a cool easy-to-show fact that you can never make something hotter than the light source my focusing its light.
Since otherwise you could take heat and divide it into a hotter and colder region, decreasing entropy without using energy.

[-] nicoweio@lemmy.world 3 points 10 months ago

I'm not sure about the easy-to-show part, but take a look at the Brightness Theorem / Conservation of https://en.wikipedia.org/wiki/Etendue if you want to learn more.

[-] Redjard@lemmy.dbzer0.com 3 points 10 months ago

The easy to show part was the second sentence of my comment.

This is really useful physics trivia, because the basic truth is easy to show from a simple law, but the detailed explanations go quite in-depth.

With lenses, you trade bewteen angular accuracy and light density.

For a challenge, try it with LEDs. Where do you find the source "temperature", you can get from focusing an LEDs light?

[-] nicoweio@lemmy.world 2 points 10 months ago

That's an intriguing question. My first guess would be it corresponds to the diode's band gap?

[-] Redjard@lemmy.dbzer0.com 1 points 10 months ago

Thats definitely hugely relevant, yes.

this post was submitted on 15 Feb 2024
457 points (95.4% liked)

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