Typically this probability depends on the temperature $T$. We only have a probability that a particular number is exchanged. How does the temperature enter in all this? Roughly speaking, in many situations we're actually uncertain about the number of photons exchanged by the electromagnetic field. So if the same number of photons is exchanged in two different situations, through equal areas and in equal amounts of time, the intensity can still be different in the two situations. The energy of a photon depends on the frequency $\nu$ of the electromagnetic field exchanging it: the energy is $h\nu$, where $h$ is Planck's constant. We speak of "quanta" of energy because the electromagnetic field cannot give or receive energy continuously, but only in multiples of a minimum amount – the quantum, the photon.īut this isn't the full story. So by definition the energy exchanged is proportional to the number of photons, and therefore the light intensity is proportional to the number of photons exchanged through a surface, divided by the surface area and the time of the exchange. The problem is that the statement is a little imprecise, so it has some truth and some falsity.Ī photon is, by definition, a quantum of energy exchanged between the elecromagnetic field (more precisely: a mode of the electromagnetic field) and something else. Cheers, everyone :D! Thank you so much for giving me your time! intensity of light coming from a BLACK BODY does increase, regardless of whether we're studying classical theories or quantum theories. And, finally, Plank's Quantum Theory is correct for all wavelengths. Classical physics is correct in predicting the behavior of radiation emitted when the body was heated, but only to specific wavelengths. fact of the matter is, when we're discussing BLACK BODY RADIATIONS, specifically, the intensity of light does increase with temperature, regardless of whether you're considering classical or quantum physics. UPDATE: I might have, sort of, figured it out. intensity of a photon isn't dependent on temperature IN QUANTUM PHYSICS. But when you're solely talking about a photon, Stefan's law doesn't apply and so. So, when you're talking about the macro-level, AKA, a body emitting light as some of the answers here explain, Stefan's law applies. UPDATE: I asked my teacher this question and he explained that Stefan's law applies when we're restricted to Classical Physics, not Quantum Physics. technically, isn't intensity also non-linearly dependent upon temperature? But then, what about Boltzmann's law? Isn't intensity dependent on the fourth power of absolute temperature?Įven if you only consider temperature, we do observe that even though intensity is non-uniformly changed, increasing temperature does increase the MAXIMUM intensity. Recently, my teacher just told us that intensity is not linearly dependent on temperature and that it's ONLY dependent on photons.
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