Question 23M.3.HL.TZ1.7
| Date | May 2023 | Marks available | [Maximum mark: 5] | Reference code | 23M.3.HL.TZ1.7 |
| Level | HL | Paper | 3 | Time zone | TZ1 |
| Command term | Explain | Question number | 7 | Adapted from | N/A |
gamma-ray photon of frequency is emitted from the top T of a tower towards the base B of the tower.
Explain, by reference to the equivalence principle, why the frequency of the photon measured at B will be larger than .
[3]
according to the EP the tower is equivalent to a frame accelerating away from Earth «with a = g» ✓
an observer at B approaches the source of light ✓
and so by the Doppler effect must measure a higher frequency ✓
Award [1] for correct explanation without principle of equivalence
Photon in a gravitational field. In a), many students explained the frequency without referring to the equivalence principle.
Two identical clocks at T and B use the period of a light wave to measure time intervals.
Explain whether observers at T observe the clock at B to be running slower or faster.
[2]
«the clock at B» runs slower «than T» ✓
the period at B is shorter since frequency is higher
OR
Clock B is in a stronger gravitational field than T
OR
the wave red shift when travelling up ✓
b) was answered quite well.