Spectroscopy – Section 1

11. Which of the following components of a monochromator is the dispersing element?

A. The collimating lens
B. The entrance slit
C. The diffraction grating
D. None of these

Correct Answer: C. The diffraction grating
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12. A simple harmonic oscillator may absorb energy

A. at any time.
B. when the frequencies match exactly
C. when the amplitudes are the same.
D. at no time.

Correct Answer: B. when the frequencies match exactly
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13. UV-Vis spectroscopy of organic compounds is usually concerned with which electronic transition(s)?

A. σ → σ*
B. n → σ*
C. n → π* and π → π*
D. none of these

Correct Answer: C. n → π* and π → π*
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14. Vibrational spectroscopy is

A. a large mass on a weak spring
B. a flashlight through a prism and shake it
C. a class of spectroscopic techniques which analyzes molecular motions
D. an Infrared spectroscopy

Correct Answer: C. a class of spectroscopic techniques which analyzes molecular motions
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15. Why are rotational transitions of little use to a spectroscopist?

A. Because the energy required to induce a rotational transition is so small that it cannot be measured
B. Because rotational transitions are extremely rare
C. Because, in liquids and solids, spectral lines corresponding to rotational transitions are broadened as the result of molecular collisions and other interactions
D. All of the above

Correct Answer: C. Because, in liquids and solids, spectral lines corresponding to rotational transitions are broadened as the result of molecular collisions and other interactions
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