A-LevelPhysicsMedical physics9702/41 · May/June 2019 · Q95 Marks
Nuclear magnetic resonance imaging (NMRI) is used to obtain diagnostic information about internal body structures. State, during the use of NMRI, the function of:
- (a)the large constant magnetic field[3]
- (b)the non-uniform magnetic field.[2]
Mark scheme
Marking points from the official mark scheme (May/June 2019). The mark or mark type is shown in brackets.
- [1] nuclei precess
- [1] precession is about direction of magnetic field
- [1] frequency of precession depends on field strength or frequency of precession is in radio-frequency range
- [2] Any two points from: • frequency (of precession) depends on position to locate position of (spinning) nuclei to change region where nuclei are detected
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