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Planck and Quantum Theory (1 Viewer)
- Thread starter Cheezy-G
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plancks's idea of black body radiation was that when radiation was absorbed by the black body, it would let out the heat or radiation or whatever at a constant rate, (not proportional). this was disproved...because, when looked at the rate it released radiation, there was a peak in the graph and then a decline. look in the jacaranda physics book, its got good diagrams
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you don't need to worry about a technical explanation (because it's beyond high school and involves statistical electrodynamics), all you need to know is that since the experimental data did not agree with the classical Rayleigh-Jean curve for black body radiation, then obviously something is wrong with the classical theory. so, in comes Planck with his brilliant mind, and he solved the problem (entirely via mathematics) by imagining that the black body is a congregation of harmonic oscillators which liberate EMR in discrete amounts or packets. with this "assumption" he then went on to produce a black body equation which successfully complied with experimental observations --> which conversely proved that his original assumption of harmonic oscillators was correct.
so therefore, his idea of releasing energy in discrete packets was vindicated and he names these packets of energy "quanta".
so ie. his assumption of the quanta led to a black body radiation curve that fitted the experimental model.
additional point you can argue for planck's results: the classical black body radiation curve could NEVER have been correct anyways, even without experimental data to tell us that. Why? Because of the Law of Conservation of Energy---> you see, the classical curve for Intensity verses Wavelength never CUTS any axis (ie. 'x' or 'y') as wavelength approaches 0, as a consequence, the AREA under the curve from 0 wavelength to infinity in indeed INFINITE for ALL TEMPERATURE settings, but the area represent the energy dissipation of the black body! so if the classical curve was correct then it means that at ANY temperature, the black body will emits (for no reason) or dissipate an infinite amount of energy ---> which clearly is nonsense and violates Energy Conservation! so this is why the classical graph could not have been right at first sight anyways.
the proper curve actually bends back and cuts the x-axis as the wavelength approaches 0, and if you measure the area (through integration) between this x-intercept to a wavelength of inifinity then you will actually arrive at a FINITE LIMITING SUM ---> which means the energy dissipation is constant but conserved, and that makes sense.
hope i helped here
so therefore, his idea of releasing energy in discrete packets was vindicated and he names these packets of energy "quanta".
so ie. his assumption of the quanta led to a black body radiation curve that fitted the experimental model.
additional point you can argue for planck's results: the classical black body radiation curve could NEVER have been correct anyways, even without experimental data to tell us that. Why? Because of the Law of Conservation of Energy---> you see, the classical curve for Intensity verses Wavelength never CUTS any axis (ie. 'x' or 'y') as wavelength approaches 0, as a consequence, the AREA under the curve from 0 wavelength to infinity in indeed INFINITE for ALL TEMPERATURE settings, but the area represent the energy dissipation of the black body! so if the classical curve was correct then it means that at ANY temperature, the black body will emits (for no reason) or dissipate an infinite amount of energy ---> which clearly is nonsense and violates Energy Conservation! so this is why the classical graph could not have been right at first sight anyways.
the proper curve actually bends back and cuts the x-axis as the wavelength approaches 0, and if you measure the area (through integration) between this x-intercept to a wavelength of inifinity then you will actually arrive at a FINITE LIMITING SUM ---> which means the energy dissipation is constant but conserved, and that makes sense.
hope i helped here