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Blackbody

Blackbody. A black body is an ideal system that absorbs all radiation incident on it The electromagnetic radiation emitted by a black body is called blackbody radiation. Stefan’s law. Wien’s displacement law λ max T = 2.898 x 10 -3 m.K.

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Blackbody

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  1. Blackbody A black body is an ideal system that absorbs all radiation incident on it The electromagnetic radiation emitted by a black body is called blackbody radiation Stefan’s law • Wien’s displacement law • λmaxT = 2.898 x 10-3 m.K

  2. In 1900 Planck developed a theory of blackbody radiation that leads to an equation for the intensity of the radiation (see in the class how to take limits). This equation can fit with experimental data Max Planck • h = 6.626 x 10-34 J.s • h is a fundamental constant of nature

  3. Photoelectric Effect The emitted electrons are called photoelectrons

  4. Compton Effect

  5. Compton shift equation The shifted peak, λ’ is caused by the scattering of free electrons The graphs show the scattered x-ray for various angles • Compton wavelength is

  6. Emission Spectra Absorption Spectrum

  7. In 1885, Johann Balmer found an empirical equation that correctly predicted the four visible emission lines of hydrogen • Hα is red, λ = 656.3 nm • Hβ is green, λ = 486.1 nm • Hγ is blue, λ = 434.1 nm • Hδ is violet, λ = 410.2 nm • RH is the Rydberg constant • RH = 1.097 373 2 x 107 m-1 • n is an integer, n = 3, 4, 5,…

  8. Lyman series: Paschen series: Brackett series:

  9. Rutherford J. J. Thomson Formal student of Thomson At Cambridge Marsden Geiger Rutherford worked with his students at the U of Machester Raisin cake

  10. Arrival of the Quantum Hero, Niels Bohr He knew that the work of Planck and Einstein on light radiation was very important, , not just clever German ideas. Until he discovered the Balmer series by mixing classical and quantum physics, also using two postulations: (see proof in the class) 1. 2.

  11. postulated that because photons have both wave and particle characteristics, perhaps all forms of matter have both properties Louis de Broglie He predicted the wave nature of electrons The de Broglie wavelength of a particle “Electron standing waves in an atom only certain Wavelengths will fit around a circle”

  12. In his thesis, he started with Einstein’s Formula Wavelength decreases as momentum increases One of his committee (Paul Langevin) had forwarded his thesis to Einstein

  13. Electron Diffraction The slit widths are small compared to the electron wavelength

  14. Davisson-Germer Experiment If particles have a wave nature, then they should exhibit diffraction effects Bragg’s Law

  15. Wave packet • The phase speed of a wave in a wave packet is given by • This is the rate of advance of a crest on a single wave • The group speed is given by • This is the speed of the wave packet itself

  16. Werner Heisenberg Solve problems in the class and tutoring class

  17. Erwin Schrodinger The Schrödinger equation as it applies to a particle of mass m confined to moving along the x axis and interacting with its environment through a potential energy function U(x) is This is called the time-independent Schrödinger equation

  18. A Particle in an infinite potential well The lowest allowed energy corresponds to the ground state En = n2E1 are called excited states E = 0 is not an allowed state, The particle can never be at rest

  19. A Particle in a finite potential well

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