Black Body Radiation


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BridgetJ_2J
Posts: 16
Joined: Wed Sep 21, 2016 2:56 pm

Black Body Radiation

Postby BridgetJ_2J » Fri Sep 30, 2016 1:51 pm

Can someone explain to me what black body radiation is and its significance to what we're currently learning (or to the class in general)?

Jasmine Cha 1A
Posts: 22
Joined: Wed Sep 21, 2016 2:59 pm

Re: Black Body Radiation

Postby Jasmine Cha 1A » Fri Sep 30, 2016 1:59 pm

From what Professor Lavelle mentioned, we won't really need to use black body radiation regularly, I believe. However, black bodies are just a hypothetical term for materials that absorb all frequencies (but no material actually does this). It was just mentioned as a contrast to atoms since, unlike black bodies, atoms have a unique spectrum of frequencies that they can absorb.
If I'm wrong, someone can definitely correct me on this though.

Daniel_Callos_4I
Posts: 16
Joined: Wed Sep 21, 2016 2:57 pm

Re: Black Body Radiation

Postby Daniel_Callos_4I » Fri Sep 30, 2016 2:33 pm

I read on the topic and asked Dr. Lavelle during office hours, and I think this is how it goes. As mentioned above and in the course reader, black bodies are different from atoms and molecules in that atoms and molecules have characteristic absorption and emission spectra; however, black bodies can absorb and emit radiation at all frequencies. Traditional theory stated that, as an object absorbed and emitted radiation, it would emit energy in the form of radiation predominantly at higher frequencies. This means that black bodies could glow with damaging UV or gamma rays, which is contradictory to common sense. Moreover, by means of integration, if you were to sum the total energy emitted, you would find that the total emitted energy is infinite (in math speak, the integral does not converge). This is in violation of basic thermodynamics and led to a reconsideration of the way in which objects absorb and emit energy.
It was later realized that such bodies mainly gave off radiation in the visible spectrum, and not in the UV or gamma spectra. based on heuristic evidence observed by Planck. FWhen Planck tried to curve-fit this data, the number 6.626*10^(-34) [Planck's constant] came up. This entire process required new evidence for this novel behavior of light and served as an important precursor for photoelectric experimentation.
Hope this helps and happy chemistry!

-Dan Callos


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