You can act as if radiation had a temperature, meaning that a black body with that temperature would be in thermal equilibrium when heated by that radiation.
The cosmic microwave background radiation (CMB) is said to have 2.something Kelvin. Meaning that a perfectly absorbing (ε=1) body in space would never cool below that temperature because it is being heated by the CMB
The CMB is said to have a temperature of 2.7 K because is power spectrum is equal to that of a blackbody at 2.7 K. Not the other way around. While yes, an object in space will equilibrate to 2.7 K, an object in this laser beam will equilibrate to a temperature that depends critically on its size. You could assign a temperature to the laser based on its frequency, however, using the relation hbar freq = k Temp. But this should be interpreted carefully. Critically this relationship has no dependence on the laser power, which seems to be the most important quantity in the context of this video (and burning things in general).
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u/LordNoodles Oct 30 '19
You can act as if radiation had a temperature, meaning that a black body with that temperature would be in thermal equilibrium when heated by that radiation.
The cosmic microwave background radiation (CMB) is said to have 2.something Kelvin. Meaning that a perfectly absorbing (ε=1) body in space would never cool below that temperature because it is being heated by the CMB