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UV Luminance Spectroscopy (Biochemistry) Question and Answers-Page first

UV Luminance Spectroscopy problems


  • 1. What is the relationship between wavelength and wave number?

  • Options
  • A. Wavenumber = 1 / wavelength in centimeters
  • B. Wavenumber - wavelength in nanometers = 1
  • C. Wavelength in nanometers x wavenumber = 1
  • D. None of the above
  • Discuss
  • 2. Why must the radiation source for fluorescence spectrometry be more powerful than for absorption spectroscopy?

  • Options
  • A. Because the magnitude of the output signal is proportional to the power of the incident radiation
  • B. Because the sample won't fluoresce if the incident radiation is of low power
  • C. To allow for scattering by the sample
  • D. None of the above
  • Discuss
  • 3. Why phosphorescence measurements are usually made at a low temperature?

  • Options
  • A. To prevent thermal degradation of the phosphorescent species
  • B. To promote phosphorescence by slowing the rate of radiationless transfer processes
  • C. To increase the efficiency of the detector
  • D. To decease the efficiency of detector
  • Discuss
  • 4. In the intersystem crossing

  • Options
  • A. the spin of an excited electron reverses, changing the state of the molecule (from singlet state to triplet state or vice versa)
  • B. a molecule converts its excess energy to light, and emits a photon
  • C. a molecule converts excess electronic energy to vibrational energy
  • D. all of the above
  • Discuss
  • 5. For a molecule to absorb IR, why must the molecule's vibrations cause fluctuations in the dipole moment of the molecule?

  • Options
  • A. Because a change in dipole moment lowers the energy required for electronic transitions
  • B. Because for absorption to occur, the radiation must interact with the electric field caused by changing dipole moment
  • C. Because fluctuations in the dipole moment allow the molecule to deform by bending and stretching
  • D. All of the above
  • Discuss
  • 6. Why do fluorescence spectrometers often use double-beam optics?

  • Options
  • A. So a reference solution can be used
  • B. To compensate for beam attenuation by the monochromator
  • C. To compensate for power fluctuations in the radiation source
  • D. All of the above
  • Discuss
  • 7. Fluorescence occurs when

  • Options
  • A. a molecule returns to the electronic ground state from an excited triplet state by losing it's excess energy as a photon
  • B. a molecule returns to the electronic ground state from an excited singlet state by losing it's excess energy as a photon
  • C. a molecule lowers its vibrational energy by losing it's excess energy as a photon
  • D. none of the above
  • Discuss
  • 8. Internal conversion is where

  • Options
  • A. the spin of an excited electron reverses, changing the state of the molecule (from singlet state to triplet state or vice versa)
  • B. A molecule converts its excess energy to light, and emits a photon
  • C. A molecule converts excess electronic energy to vibrational energy
  • D. none of the above
  • Discuss

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