Card Set Information

2012-11-26 12:30:35
ME 627

Show Answers:

  1. Spectral Reflectance and emittance changes with..
    Wavelength and temperature
  2. Spectrale reflectance and emission may also change with...
    Light polarization and surface roughness/condition
  3. Emittance: For spectral, directional, hemispherical analysis...
    Directional average of e' over outgoing directions
  4. Emittance: Total directional
    Spectral average of e'
  5. Emittance: Total Directional, hemispherical
    Directional and spectral average of e'
  6. Aborptance depends on?
    Incoming intensity.
  7. Spectral, hemispherical absorptance...
    Depends on incoming radiation (and therefore entire temperature field), so it is not a pure surface property
  8. For blackbodies, what does spectal emissive power depend on?
    Wavelength and temp. only
  9. For real surfaces, what does emissive power depend on?
    Direction of the observer to the surface (characterized by theta and/or the vector s).  
  10. For recombining plasma
    Texc > Teq
  11. For Ionizing plasma..
    T exc < Teq
  12. Boltzmann Distribution
    Texc = Teq
  13. For thermodynamic equilibirum..
    • -Each process is balanced with its reversed process.
    • -Radiation follows the Planck formula
  14. For technical processes, LTE
    • LTE= local thermal equilbirum.
    • Collisions dominate excitation at higher pressure
    • Boltzmann distribution are valid
  15. Describe Spontaneous emission
    Excited state is created, and photon emitted in an arbitrary direction
  16. Describe Induced emission:
    • delta e=hv already hits an excited stated,
    • "induced emossion is emitted in the same direction as the incoming photon.
  17. Descroibe LASER (Light Amplification by Stimulated Emission of Radiation)
    • -Excited states generated through pump source
    • -Induced emission is containted in a cavity through mirriors
    • -Standing wave is formed to maintain the simululated emission process
    • -Part of the standing wave is extracted through one side of the cavity
  18. Emission characterizes the upper state (T or F)
  19. Absorption characterizes the lower state (T or F)
  20. What does absorption lead too?
    An exponential decrease of incident radiation
  21. Define line strength
    It is the spectral integration over the absorption coefficient.  
  22. What four processes may emission and absorption lines be broadened through?
    • 1) Natural Broadening
    • 2) Doppler Broadening
    • 3) Collisional Broadening
    • 4) Zeeman Broadening
  23. Describe the Doppler Effect.
    It states that a wave moving from an emitter will increase in frequency if the emitter is moving towards the observered.

    It will decrease in frequency if it is moving away.
  24. Describe the three factors in collision broadening:
    • 1) Van der Waals: collision with neutrons
    • 2) Resonance: collisions with "like" species particles
    • 3) Stark: Interactions with ions or electrons. ¬†Specific for each transition/line
  25. Describe a Gauss profile:
    Half widths of a gauss can be combined quadratically.

    99% of transition energy reached in 2 HWHM
  26. Describe a Lorentz profile:
    Half widths of Lorentz profile can be summed linearly.

    90% of transition energy within 6 FWHM

    99% is reached after 50 HWFW
  27. Voigt Broadening
    Used when both a Gauss and Lorentz is present.

    Combination of one Gauss and one Lorentz width.