1 / 18

Waves, Light & Quanta

Waves, Light & Quanta. Tim Freegarde. Web Gallery of Art; National Gallery, London. electron wavelength. Davisson-Germer experiment. NICKEL TARGET. C Davisson & L H Germer, Phys Rev 30 705 (1927). ELECTRON DIFFRACTION. electrons behave like waves. Diffracting atoms.

daria-castaneda
Télécharger la présentation

Waves, Light & Quanta

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Waves, Light & Quanta Tim Freegarde Web Gallery of Art; National Gallery, London

  2. electron wavelength Davisson-Germer experiment NICKEL TARGET C Davisson & L H Germer, Phys Rev 30 705 (1927) ELECTRON DIFFRACTION • electrons behave like waves

  3. Diffracting atoms E M Rasel et al, Phys Rev Lett 75 2633 (1995)

  4. molecule wavelength Diffracting molecules S Gerlich et al, Nature Physics 3 711 (2007) MOLECULE DIFFRACTION • molecules behave like waves

  5. + • circular orbits Bohr model of the hydrogen atom BOHR MODEL • quantized angular momentum • de Broglie wavelength • quantized energy levels • Hydrogen energy level measurements and calculations agree to 15 figures

  6. energy quantized in units of (h = Planck’s constant) • momentum quantized in units of • frequency determined by energy • de Broglie wavelength determined by momentum • angular momentum quantized in units of • angular momentum quantized in units of PHOTONS Quantum theory • blackbody radiation • photoelectric effect • Compton scattering PARTICLES • electron diffraction • atomic theory

  7. + • circular orbits Bohr model of the hydrogen atom BOHR MODEL • quantized angular momentum • de Broglie wavelength • quantized energy levels • Hydrogen energy level measurements and calculations agree to 15 figures

  8. energy • allowed energies 0 n = 3 n = 2 n = 1 Bohr model of the hydrogen atom n =  Rydberg constant • emission wavelengths

  9. energy • allowed energies n =  0 n = 3 n = 2 n = 1 Atomic line spectra Rydberg constant • emission wavelengths

  10. n =  energy n = 3 0 n = 2 universe-review.ca scope.pari.edu n = 1 Atomic line spectra Paschen Balmer Lyman

  11. energy • allowed energies 0 n = 3 n = 2 n = 1 Hydrogenic atoms n =  Rydberg constant • emission wavelengths

  12. singlet triplet Hg J Franck & G Hertz, Verh. Dtsch. Phys. Ges. 16 457 (1914) Franck-Hertz experiment • accelerate electrons through atomic vapour • periodic modulation of measured current • inelastic collisions when electron energy equals atomic transition energy G Rapior et al., Am J Phys 74 423 (2006)

  13. energy quantized in units of (h = Planck’s constant) • momentum quantized in units of • frequency determined by energy • de Broglie wavelength determined by momentum • angular momentum quantized in units of • angular momentum quantized in units of PHOTONS Quantum theory • blackbody radiation • photoelectric effect • Compton scattering PARTICLES • electron diffraction • atomic theory • Stern-Gerlach • discrete energy levels for bound particles • atomic theory

  14. SPONTANEOUS EMISSION energy 0 n = 3 n = 2 STIMULATED EMISSION n = 1 Quanta: absorption and emission of photons ABSORPTION n =  ABSORPTION absorption emission

  15. SPONTANEOUS EMISSION • thermal equilibrium STIMULATED  blackbody spectrum EMISSION • amplification of light if atomic population is inverted i.e. Quanta: absorption and emission of photons ABSORPTION EINSTEIN EQUATIONS • Einstein A and B coefficients ABSORPTION • spontaneous emission stimulated by vacuum field

  16. Waves, Light & Quanta: the LASER LIGHT AMPLIFICATION by Stimulated Emission of Radiation • Theodore Maiman, 16 May 1960 mirror beam splitter 693.4 nm ruby flash tube light amplifier optical resonator

  17. energy Waves, Light & Quanta: the ruby LASER mirror beam splitter 693.4 nm ruby flash tube metastable light amplifier optical resonator • Cr3+ ions in sapphire (Al2O3) absorb blue and green from flash light absorption emission • internal transitions to metastable state Cr3+ • spontaneous emission is amplified by passage through ruby • repeatedly reflected/amplified near-axial light builds up to form coherent laser beam

  18. mirror beam splitter ruby flash tube • narrow linewidth for long pulses ( ) Waves, Light & Quanta: beam characteristics 693.4 nm • as initial source recedes down unfolded cavity, emission approaches that from distant point source • divergence determined by diffraction by limiting aperture • focusable • constructive interference between reflections for certain wavelengths • long pulse  continuous wave (c.w.) • monochromatic • noise from spontaneous emission gives lower limit to linewidth • nonlinear processes have various effects in detail • Hecht section 13.1

More Related