A few questions on blackbody radiation

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Homework Statement

Suppose we have a copper foil at room temperature 300 K°, in the dark.

If we irradiate it on both sides with laser beams at frequency , say 10^ 13 Hz, one would expect a temp of 500 K° and EMR at 10^ 13.

Actually it radiates , according Plancks law, at higher frequencies up to visible light
over 4x 10^ 14 Hz.
Where does the surplus energy come from?

What happens when EMR hits the surface?

please say if these statements are right or wrong:

1) protons oscillate at 10^13 and pass on oscillation to inner protons
2) neutrons oscillate but do not emit radiation
3) electrons jump to outer orbits and fall back realeasing radiation
4) only the outside one free electron jumps up and down
5) the other electrons do not absorb energy
6) the inside free electron flow inside the foil toward cooler atoms

One would think that, whatever the answer to these and other aspects I ignored and you
might add, the highest level of energy is 10^ 13

so WHO is oscillating in visible spectrum, only outer fre electrons?
and where does the energy come from, certainly not from laser or room!



II) suppose the volume of foil 1 mm^3
how do we calc total energy?
I read Stefan's law says it depends only on Temp^4 is it sigma 6.25x 10^10 ( what? Joules?)
if volume doubles, what happens?

 

[mark726]

Thank you for your interesting post. I would like to offer some clarifications and corrections to the statements and questions you have presented.

Firstly, it is important to note that the temperature of an object is not solely determined by the frequency of the radiation it is exposed to. Other factors, such as the intensity and duration of the radiation, also play a role.

Now, to address your statements and questions:

1) Protons do not oscillate at a frequency of 10^13 Hz. The frequency of oscillation for protons is much higher, in the range of 10^20 Hz. Additionally, protons do not pass on oscillation to inner protons.
2) Neutrons do not emit radiation, but they can absorb radiation and change their energy states.
3) Electrons do not jump to outer orbits and fall back to emit radiation. This concept is based on the outdated Bohr model of the atom. In reality, electrons exist in a probability cloud around the nucleus and do not have set orbits.
4) All electrons in an atom can absorb and emit radiation, not just the outermost one. However, the outermost electrons are typically the most energetic and therefore more likely to emit radiation.
5) Electrons can absorb energy from radiation, but they can also transfer that energy to other particles in the material through collisions.
6) The movement of electrons within the material is not determined solely by the temperature or radiation exposure. The behavior of electrons is more complex and is influenced by various factors such as the material's properties and external forces.

To calculate the total energy of the foil, one would need to consider the energy of all the particles within the material, including protons, neutrons, and electrons. This would require a detailed analysis and calculation, taking into account the specific properties of the material.

Stefan's law relates the total energy radiated by an object to its temperature. It is usually expressed as the Stefan-Boltzmann law, which states that the total energy radiated per unit time by a blackbody is proportional to the fourth power of its temperature. The constant of proportionality is known as the Stefan-Boltzmann constant, which has a value of approximately 5.67 x 10^-8 W/(m^2*K^4).

If the volume of the foil doubles, the total energy radiated would also increase. However, this increase would not be proportional to