Photo AI
Figure 2 shows the distribution of kinetic energies of $eta^-$ particles from the decay of carbon-14 - AQA - A-Level Physics - Question 2 - 2022 - Paper 1
Question 2
Figure 2 shows the distribution of kinetic energies of $eta^-$ particles from the decay of carbon-14. Explain how Figure 2 supports the existence of the antineutri... show full transcript
Worked Solution & Example Answer:Figure 2 shows the distribution of kinetic energies of $eta^-$ particles from the decay of carbon-14 - AQA - A-Level Physics - Question 2 - 2022 - Paper 1
Step 1
Explain how Figure 2 supports the existence of the antineutrino.
Answer
Figure 2 shows a distribution of kinetic energies of eta^- particles emitted from the decay of carbon-14. The presence of a peak in the distribution indicates that particles have a range of energies, but the distribution does not account for all the energy released in the decay process. This suggests that there is another particle, the antineutrino, carrying away the missing energy. The variability in the energies of the emitted eta^- particles, with their maximum energy being lower than expected, supports the idea that an undetected particle is present, which is consistent with the existence of the antineutrino.
Step 3
Deduce which three gamma photons could have been produced by positron annihilation.
Answer
In the annihilation process, the positron and an electron produce two gamma photons, each with energy equal to the rest mass energy of the particles involved. The energy of each photon produced can be calculated as:
Thus, two gamma photons would have an energy of:
However, in addition to these two photons, a third photon can be produced from excess energy in the system. From Table 1, we see that only G3 with energy J corresponds to an energy that could be relevant to this annihilation scenario, given sufficient energy could be available from the interaction.