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.
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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.
If a sample is placed in an applied magnetic field, the net magnetic moment of the sample will:
A. a) Be zero, due to the large number of spins and random orientation of vectors.
B. b) Align along the direction of the applied magnetic field.
C. c) Will have no preferred orientation.
Why does clinical MRI detect the magnetic resonance signal of water protons in the body?
A. a) Because only water protons have spin.
B. b) Because water has an odd number of neutrons.
C. c) Because water protons are the most abundant spins in the body.
How much energy is converted into heat by an electron beam in an X-ray tube?
A. 1%
B. 10%
C. 99%
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