A 90 degree pulse aligned along the X-axis is applied creating transverse magnetization. In the rotating frame of reference, if a 180 degree pulse aligned along the X-axis is then applied after a time tau, the vectors will rotate:
A. ) 180 degrees around the X-axis.
B. ) 180 degrees around the Y-axis.
C. ) 180 degrees around the Z-axis.
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When the spin vectors in the transverse plane have completely randomized due to dephasing:
A. a) the net magnetization is zero within the transverse plane.
B. b) the net magnetization is increased within the transverse plane.
C. c) the net magnetization remains unchanged.
Considering the effect of an RF pulse on the net magnetization, the higher the power of the RF field:
A. a) the slower the rotation and smaller the pulse angle.
B. b) the slower the rotation and larger the pulse angle.
C. c) the faster the rotation and larger the pulse angle.
When viewed in the rotating frame, spin vectors precessing at the Larmor frequency:
A. a) appear to precess at the Larmor frequency.
B. b) appear to precess slower compared to an observer in the laboratory.
C. c) appear to be stationary and not precessing.
The number of spins existing in the two different energy levels, at any one time, is determined by:
A. a) The energy difference between the levels and the temperature of the system.
B. b) The number of protons only.
C. c) The number of energy levels.
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