Questions About Stefan-Boltzmann Law

In summary: The 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 which has less energy than photon at 0,6.
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mp44
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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?
 
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mp44 said:
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.
I forgot to say: are you sure about that number?
 
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DrClaude said:
I forgot to say: are you sure about that number?
Pretty sure,the energy increases with temperature on the 4th,about Planck's law-my english is not that good
 
  • #5
mp44 said:
Pretty sure,the energy increases with temperature on the 4th
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.

mp44 said:
about Planck's law-my english is not that good
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
DrClaude said:
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.
Sorry,that is what I ment,my mistake.

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.
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 which has less energy than photon at 0,6.
 

1. What is the Stefan-Boltzmann Law?

The Stefan-Boltzmann Law is a physical law that describes the relationship between the temperature and the amount of thermal radiation emitted by a black body. It states that the total energy radiated per unit surface area of a black body is proportional to the fourth power of its absolute temperature.

2. Who discovered the Stefan-Boltzmann Law?

The Stefan-Boltzmann Law was discovered by Austrian physicist Josef Stefan in 1879. Later, in 1884, it was further developed and generalized by physicist Ludwig Boltzmann.

3. What is a black body?

A black body is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of the wavelength or angle of incidence. It also emits thermal radiation based on its temperature and follows the Stefan-Boltzmann Law.

4. What are some real-life applications of the Stefan-Boltzmann Law?

The Stefan-Boltzmann Law has many real-life applications, including determining the surface temperature of stars, calculating the heat transfer in buildings and other structures, and understanding the energy balance of Earth's atmosphere.

5. How is the Stefan-Boltzmann Law related to the greenhouse effect?

The Stefan-Boltzmann Law is related to the greenhouse effect because it helps to explain how the Earth's atmosphere absorbs and emits thermal radiation. The greenhouse effect is caused by certain gases in the atmosphere, such as carbon dioxide, which absorb and re-emit thermal radiation, trapping heat and keeping the Earth's temperature at a habitable level.

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