4 ms·
Black body photons are coming at random times. Laser photons are coherent, so are timed. Think of swing - if you try to push it randomly you'll get it swing as
by skolos 8y ago
Black body photons are coming at random times. Laser photons are coherent, so are timed. Think of swing - if you try to push it randomly you'll get it swing as far as hardest push. But if you push periodically, you can swing it very far with small pushes.
- empiricus 8y agoThanks. So the laser is really special; because it is coherent it can be absorbed and transformed into heat without limit. <br> For random photons, no matter the light intensity, there is a limit temperature of the receiver, which depends on the photon spectrum... <br> From this point of view (energy transfer) are there more than these two kinds of light?
- MRD85 8y agoBut won't two hard pushes in a row send you flying? I would have presumed you could find the mean and standard deviation of both the energy of the pushes and the frequency of the pushes and you could build a model to find the expected height.
- darkmighty 8y agoThat's not important at all; what's important is that black body radiation has a fixed maximum flux -- its spectrum or lack of coherence isn't why you can't heat another body to a greater temperature. It comes back to etendue, or if you prefer the 2nd law. You could reproduce any fixed black body spectrum (to arbitrary accuracy) from a set of thermal sources and filters (or a set of lasers, LEDs, etc. with random phases) to arbitrary fluxes just like a laser has, and use this light to heat objects to arbitrary temperature. But if the original emission is of black-body type, you cannot -- the flux is given by the quantum mechanical process and a function of local temperature only. From then it follows from etendue conservation you cannot achieve higher temperatures.
- empiricus 8y agoInteresting, this makes more sense. Now I have to read more on the conservation of entendue.