# Stefan-Boltzmann law

1. Feb 17, 2015

### mp44

Hi, I have a few questions about Stefan-Boltzmann's law. Let's say that the temerature of an object increases for 2 degrees Celsius, that means that the emmited energy of a surface of that object will increase 16 times. Is this happening because the number of photons is increased 16 times or is the energy of 1 photon increased 16 times or something in between? What is the correlation between temperature of an object and the number of photons it emmits (if one exists)? Let's say in the example of light bulb, if the temerature of a light bulb increases will the light bulb glow brighter, and if it does is it because of an increase of a number of photons or the increase of the energy of 1 photon?

2. Feb 17, 2015

### Staff: Mentor

Last edited by a moderator: May 7, 2017
3. Feb 17, 2015

### Staff: Mentor

I forgot to say: are you sure about that number?

4. Feb 18, 2015

### mp44

Pretty sure,the energy increases with temperature on the 4th,about Planck's law-my english is not that good

5. Feb 18, 2015

### Staff: Mentor

But power ∝ T4 doesn't mean that if you increase by 2 K, power increases by a factor of 16. That is true if you double the temperature.

The link I gave is to Wikipedia, where you may find a version in your language. And it's about the formulas, not the text. Just look at the figure at the top, which shows spectral radiance as a function of wavelength for different temperatures.

6. Feb 18, 2015

### mp44

Sorry,that is what I ment,my mistake.
Version in my language isn't very helpful since it has only few lines,formulas don't help at all but the picture does.Let's if I got it right-spectral radiance is the density of the radiation,right? So for 5000 K spectral radiance (density) is about 12,5 for the 0,6 picometers wavelenght and for 4000 K density is 4 but also there is a decrease in energy because the most freqent wavelenght at that temperature is 1 picometers wich has less energy than photon at 0,6.