Recent content by saibod

hey, etendue seems to be an interesting buzzword! I never heard this before and should look into it.

True, that's why the solid angle reasoning is wrong! Do I understand your argument correctly that we can therefore, in particular, reach temperatures much higher than that on the sun? If yes, then this was exactly my very thinking initially. But as I tried to mention in the OP, this is not...

Thanks for your reply. But we're talking blackbody radiation here, so while not to a single photon, we can ascribe a temperature to the photon spectrum at every point in space. This is the point! There are classical limits on focussing, although these are hard to get your hands on...

cool, so you've reinvented Lagrangian field theory! Since your Lagrangian is an integral over s, is better to consider its integrand and call it a "Lagrangian density". Can you derive the Euler-Lagrange equations for a Lagrangian density? In any case, I hope you have enough buzzwords now to read...

Can one focus sunlight so much that the temperature attained at the focus is higher than the temperature on the surface of the sun? Consider this question in the framework of geometrical optics (no diffraction, no solar panels or electricity). This seemingly innocent problem is actually quite...