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Physics

Physics. Conf. Dr. Radu Fechete Technical University of Cluj-Napoca. Content 1. Davisson- Germer experiment Barrier of potential. Tunnel effect The Hydrogen atom Quantum numbers Stern and Gerlach experiment Atomic orbitals Atomic spectra Holography. Davisson- Germer experiment.

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Physics

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  1. Physics Conf. Dr. Radu Fechete Technical University of Cluj-Napoca

  2. Content 1 • Davisson-Germer experiment • Barrier of potential. Tunnel effect • The Hydrogen atom • Quantum numbers • Stern and Gerlach experiment • Atomic orbitals • Atomic spectra • Holography

  3. Davisson-Germer experiment

  4. Barrier of potential. Tunnel effect

  5. The Hydrogen atom Laguerre polynomial Legendre polynomial Quantified energy

  6. Quantum numbers n– principal quantum numbers l – orbital quantum number m – magnetic quantum number Bohr magneton

  7. Stern and Gerlach experiment Spin quantum number Energy of a magnetic moment in B

  8. Atomic orbitals

  9. Atomic spectra

  10. Atomic spectra The theory of quantum transitions -wave number Rydberg consntant H= 1.0967758  107 m-1 = 2.15  10-18 J = 13.6 eV

  11. LASERs Def: light amplification by stimulated emission of radiation Probability of spontaneous emission Probability of spontaneous absorption Boltzmann distribution Probability of stimulated emission

  12. Holography

  13. Content 2 • Semiconductors • Hall Effect • Difference of potential at metal-metal contact • Thermoelectric effect (Seebeak effect) • Magnetic materials • Diamagnetism • Paramagnetism • Ferromagnetism • Superconductivity

  14. Energetic Bands in solids

  15. Semiconductors:

  16. Hall Effect

  17. Difference of potential at metal-metal contact

  18. Thermoelectrically effect (Seebeck effect) Thermoelectrically effect consist in the apparition of an electromotive tension into a two-metals electrical circuit when a difference of temperature exist between those two contact points. The Peltier effect is considered the inverse of thermoelectric effect consisting in the heat radiation while an electrical current passes through an electical circuit consisting from two different materials:

  19. Magnetic properties of materials The total magnetic moment Sample magnetization

  20. Magnetic properties of materials H – magnetic field intensity m – magnetic susceptibility r – material relative magnetic permeability  – material magnetic permeability

  21. Substances classification • Diamagnetic: (m < 0 – small; mm(T)) • Paramagnetic ( m > 0) • Paramagnetic: ( m > 0 – small; - Curie law) • Ferromagnetic ( m > 0 – large;  m =  m(T)) • Antiferromagnetic • Ferrimagnetic.

  22. Magnetic materials: Diamagnetism The materials with no permanent magnetic moments are diamagnetic materials. The diamagnetism originates in the change of the electrons orbit in the presence of the external magnetic field.

  23. Paramagnetic materials Curie law

  24. Ferromagnetic materials Ferromagnetic materials are characterized by magnetic memory: Hysteresis curves. Hc – coercitive fields Bs – saturation field Br – remanent magnetization

  25. Ferromagnetic materials Due to the reorientation of elementary magnetic moments the sample magnetization increases with the increase of the external magnetic field. Barkhausen effect – the increase of magnetization appears in steps. Curie-Weiss law

  26. Magnetic materials Paramagnetic Ferromagnetic Antiferromagnetic Ferrimagnetic Forced ferromagnetic

  27. Superconductivity An element (inter-metallic alloy, ceramics etc.) that will conduct electricity below a certain temperature without resistance.

  28. Superconductor material:Typical structure

  29. Superconductivity : Meissner effect

  30. The origin of superconductivity Cooper pairs John Bardeen, Leon Cooper si Robert Schrieffer (BCS theory), after 60 years from the discovery of the supra-conductibility phenomena, assumes that the Cooper pairs are now bosons and are no longer subjected to the Pauli principle of exclusion. The electrons motion inside of superconductor material is perfectly ordered and the interaction with the network is much reduced.

  31. Thank You for your attention

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