1 / 28

Understanding the Physics of Light: Photons, Spectroscopy, and the Doppler Effect

This document explores key concepts in the physics of light, including the properties of photons, spectral types such as continuous, absorption, and emission spectra. It covers fundamental laws like Kirchhoff's and Planck's, and introduces the Doppler effect, explaining how motion affects observed wavelengths and frequencies. Additionally, it discusses thermal radiation, Wien's Law, and energy levels related to atomic behavior. Understanding these principles is crucial for fields like astrophysics and atomic physics, with applications in spectroscopy and light-based technologies.

astin
Télécharger la présentation

Understanding the Physics of Light: Photons, Spectroscopy, and the Doppler Effect

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. Solar Spectrum

  2. Bit of Administration …. • c = 3 x 108 m/sec = 3 x 105 km/sec • Reading • BSNV pp. 153 - 168

  3. The Physics of Light • Doppler Shift

  4. The Physics of Light • Doppler Shift • Source moving toward observer or • observer moving toward source Shorter Wavelength Higher Frequency Blueshift • Source moving away from observer or • observer moving away from source Longer Wavelength Lower Frequency Redshift

  5. The Physics of Light • Doppler Shift • Source across (perpendicular to) observer’s line of sight Same Wavelength as emitted Same Frequency as emitted No Shift Doppler Shift only provides measure of radial velocity, or speed along the line of sight

  6. The Physics of Light • Doppler Shift vrad = radial velocity of light source or observer (+ => away from each other) Dl = change (shift) in wavelength = lobserved - lrest lrest = rest wavelength c = 3 x 105 km/sec

  7. ConcepTest! When Mars is in the middle of its retrograde loop, you expect it to show A large redshift No Doppler shift A large blue shift Depends on where it is in its orbit

  8. The Physics of Light • Light as a Particle = Photons • Photon - A Discrete Unit of Light Energy • Planck’s Law h = Planck’s Constant = 6.626 x 10-34 joule sec l = wavelength in m, c = 3 x108 m/sec

  9. The Physics of Light • Light as a Particle = Photons • Planck’s Law Small wavelength Large frequency Large energy Large wavelength Small frequency Small energy

  10. The Physics of Light • Spectroscopy and Atomic Physics • Types of Spectra • Continuous - No spectral lines • Absorption - Dark lines superimposed on continuous spectrum • Emission - Isolated bright lines

  11. The Physics of Light • Spectroscopy and Atomic Physics • Kirchoff’s Laws • An opaque object emits a continuous spectrum. • An opaque object viewed through a cooler gas will produce an absorption spectrum. • A gas viewed against an empty background produces an emission spectrum

  12. The Physics of Light • Spectroscopy and Atomic Physics • Kirchoff’s Laws

  13. The Physics of Light • Spectroscopy • Temperature - a measure of the speeds of particles Room Temperature 300 oK

  14. The Physics of Light • Spectroscopy • Thermal Radiation - Any opaque object that has a • temperature above 0 oK emits light

  15. The Physics of Light • Spectroscopy • Thermal Radiation

  16. The Physics of Light • Spectroscopy • Thermal Radiation

  17. The Physics of Light • Spectroscopy • Thermal Radiation • Wien Law lmax lmax in nm T in oK

  18. Spectroscopy • Thermal Radiation • Wien Law • Stefan-Boltzmann Law The Physics of Light Eflux = energy emitted from square meter in one second • = Stefan-Boltzmann constant

  19. The Physics of Light • Spectroscopy and Atomic Physics • Kirchoff’s Laws

  20. The Physics of Light • Spectroscopy and Atomic Physics • Quantum Mechanics - Electron can only be in certain specific • orbits <=> can only have certain specific energies Quantum Numbers e Hydrogen Atom

  21. The Physics of Light • Spectroscopy and Atomic Physics • Quantum Mechanics - Electron energy changes can only have • certain values corresponding to energy changes between orbits • ==> only certain energies of photons can be absorbed or emitted

  22. The Physics of Light • Spectroscopy and Atomic Physics • Shine “white” light onto hydrogen atom White light Photons/sec Wavelength

  23. Photons/sec 660 nm Wavelength The Physics of Light • Spectroscopy and Atomic Physics • Only photons with energy equal to energy difference • between orbits 2 and 3 are absorbed. This energy • corresponds to a wavelength of 660 nm.

  24. Photons/sec 660 nm Wavelength The Physics of Light • Spectroscopy and Atomic Physics • Photons with energy equal to energy difference • between orbits 2 and 3 are emitted. These photons • are emitted in all directions.

  25. The Physics of Light • Spectroscopy and Atomic Physics • Kirchoff’s Laws

  26. The Physics of Light • Spectroscopy and Atomic Physics • Energy Level Diagrams Ground State

More Related