# Photons – Is the Intensity of Light Dependent Only on the Number of Photons?

boltzmann equationintensityphotonstemperaturevisible-light

Recently, my teacher just told us that intensity is not linearly dependent on temperature and that it's ONLY dependent on photons. But then, what about Boltzmann's law? Isn't intensity dependent on the fourth power of absolute temperature?

Even if you only consider temperature, we do observe that even though intensity is non-uniformly changed, increasing temperature does increase the MAXIMUM intensity. So.. technically, isn't intensity also non-linearly dependent upon temperature?

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. 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. But when you're solely talking about a photon, Stefan's law doesn't apply and so.. intensity of a photon isn't dependent on temperature IN QUANTUM PHYSICS. Don't know how… that works.

UPDATE: I might have, sort of, figured it out.. 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. Classical physics is correct in predicting the behavior of radiation emitted when the body was heated, but only to specific wavelengths. And, finally, Plank's Quantum Theory is correct for all wavelengths. So, yeah.. intensity of light coming from a BLACK BODY does increase, regardless of whether we're studying classical theories or quantum theories. Cheers, everyone :D! Thank you so much for giving me your time!

You are both at least somewhat right.

Photons are more or less particles of light. So the more particles, the more light. This is true at any temperature.

But making an object hot makes it emit more photons. Furthermore, it makes it emit photons of higher frequency and thus higher energy. This makes the energy go up faster than the number of photons.

There are ways of making photons other than heating an object. For example, a laser makes photons all of the same frequency. So there intensity is proportional to number of photons.