DP Physics (last assessment 2024)
Question 20N.3.HL.TZ0.18a
| Date | November 2020 | Marks available | [Maximum mark: 3] | Reference code | 20N.3.HL.TZ0.18a |
| Level | HL | Paper | 3 | Time zone | TZ0 |
| Command term | Explain | Question number | a | Adapted from | N/A |
a.
[Maximum mark: 3]
20N.3.HL.TZ0.18a
(a)
Explain the cause of the radio-frequency emissions from a patient’s body during nuclear magnetic resonance (NMR) imaging.
[3]
Markscheme
use of strong magnetic field ✓
protons are aligned ✓
radio wave at «nuclear» resonant frequency flips «some of» them into higher energy state ✓
proton de-excites emitting energy at known «radio» wavelength/frequency/Larmor frequency ✓
«which can be located and detected»
Examiners report
Candidates proved to be familiar with the use of strong magnetic fields to produce proton alignment and its consequence on excitation de-excitation of protons by emission of radio frequencies (Larmor frequency).
