Is it really true that focusing EM-waves of the same frequency, intensity, energetic density, on the same spot, we can rise temperature on that point indefinitely? I read there is a limit. Thanks.
-EDIT-: This solved my doubt because now I know formulas that simplify the understanding of how Power and Energy are linked in a luminous system...
The temperature of an object depends on the rate that heat is being added to the object and the heat that the object is losing heat to its surroundings. If you have some object at a temperature $T$ then the rate of heat loss is given by:
$$ W = kT + \sigma T^4 $$
where the first term on the right comes from Newton's law of cooling and the second term from the Stefan-Boltzmann law.
The maximum temperature of the object will be when the power radiated is equal to the power being supplied, so if the EM waves you are directing on the object have a power $P$ the maximum temperature is given by solving the equation:
$$ P = kT + \sigma T^4 $$
At very high temperatures the radiative cooling will dominate and the equation simplifies to the approximate equation:
$$ P \approx \sigma T^4 $$
or:
$$ T \approx \sqrt[4]{\frac{P}{\sigma}} $$
So, no, the temperature won't rise indefinitely. It will reach a maximum value given by the equation above.
The temperature of a body depends from the motion or vibration of the subatomic particles. Could you accelerate a subatomic particle to a greater velocity than the speed of light?
Not having any particle inside an area and shining photons of whatever intensity into this vacuum could one speak about a temperature at all?
Having a single subatomic particle in an area and fokusing intensive enough photons on this position wouldn't take place a particle creation?
It would be interesting if where are more reasons why it isn't possible to reach infinite temperature.
