Statistical Mechanics by Dr Vinay Kumar Class B
Statistical Mechanics by Dr. Vinay Kumar Class- B. Sc. (H) Physics, Section-2 Semester-VI Department-Physics and Electronics Date: 18 -03 -2020
Unit: Classical Theory of Radiation
Topic- 6. Stefan’s law
Thermodynamic Proof
Stefan-Boltzmann law
Topic- 7. Spectral Distribution of Black Body Radiation and Wien’s Displacement law Spectral distribution of black body Wien’s Displacement law According to Wien’s displacement law hot body emits the shorter wavelength and cold will emit longer wavelength
Wien’s Distribution Law According to Wien’s: Ø Resonator having velocity distribution radiation. Maxwellian emits the Ø The frequency of emitted radiation is directly proportional to kinetic energy of corresponding resonator. Ø Wien’s formula agree with experiment at short wavelength only and do not fit will at longer wavelength
Topic -8. Rayleigh-Jean’s Law According to Rayleigh. Jean’s Law : Ø He assumed that a black body radiator emits the radiation of continuously variable wavelength from 0 to ∞, and apply the law of equipartition of energy i. e. each vibration mode has average energy k. T to an oscillation.
Topic 9. Ultraviolet Catastrophe Next page for detail:
Ultraviolet Catastrophe The spectra of electromagnetic radiation emitted by hot objects. Each spectrum corresponds to a particular temperature. The black curve represents the predicted spectrum of a 5000 K black body, according to the classical theory of black bodies. At the end of the 19 th century as per classical theory (Rayleigh-Jean’s Law), the puzzle regarding blackbody radiation was that theory regarding how hot objects radiate energy predicted that an infinite amount of energy is emitted at small wavelengths, which clearly makes no sense from the perspective of energy conservation. Because small wavelengths correspond to the ultraviolet end of the spectrum, this puzzle was known as the ultraviolet catastrophe. cont/. .
Ø The German physicist Max Planck (1858 – 1947) was able to solve the ultraviolet catastrophe through what, at least at first, he saw as a mathematical trick. This trick, which marked the birth of quantum physics, also led to Planck being awarded the Nobel Prize for Physics in 1918.
Thank you
- Slides: 13