Figure 2 shows the distribution of kinetic energies of β- particles from the decay of carbon-14. Explain how Figure 2 supports the existence of the antineutrino. The existence of the antineutrino was confirmed by experiments in which antineutrinos interact with protons. The equation for this interaction is: ν̅ + p → e⁺ + X Identify particle X. The positron released in this interaction is annihilated when it encounters an electron. A pair of gamma photons is then produced. Particle X can be absorbed by a nucleus. This produces another gamma ray.

A-Level AQA Physics Classification of Particles: Figure 2 shows the distribution

Figure 2 shows the distribution of kinetic energies of β- 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 β- particles from the decay of carbon-14. Explain how Figure 2 supports the existence of the antineutrino. T... show full transcript

Worked Solution & Example Answer:Figure 2 shows the distribution of kinetic energies of β- 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.

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Answer

The distribution of kinetic energies shown in Figure 2 indicates that the β− particles emitted during the decay of carbon-14 exhibit a range of kinetic energies, with a maximum value that is not fully accounted for. This suggests that some energy is unaccounted for in the decay process. The existence of the antineutrino provides an explanation for this missing energy, as it carries away energy and momentum without being detected.

Step 2

Identify particle X.

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Answer

Particle X is a neutron.

Step 3

Deduce which three gamma photons could have been produced by positron annihilation.

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Answer

The minimum energy produced in the annihilation of the positron and electron is given by the equation:

$E = 2 imes 0.51 ext{ MeV} = 1.02 ext{ MeV} = 1.6 imes 10^{-13} ext{ J}$

Each gamma photon produced will carry energy equivalent to the total energy divided by the number of photons. Given the energies of the photons from Table 1,

G1 is $5.0 \times 10^{-14} \text{ J}$ ,
G2 is $6.6 \times 10^{-14} \text{ J}$ ,
G3 is $1.0 \times 10^{-13} \text{ J}$ .

The total energy for two photons matched the minimum energy produced, confirming that all three photons could be produced in the annihilation.

Figure 2 shows the distribution of kinetic energies of β- particles from the decay of carbon-14 - AQA - A-Level Physics - Question 2 - 2022 - Paper 1

Worked Solution & Example Answer:Figure 2 shows the distribution of kinetic energies of β- particles from the decay of carbon-14 - AQA - A-Level Physics - Question 2 - 2022 - Paper 1

Explain how Figure 2 supports the existence of the antineutrino.

Identify particle X.

Deduce which three gamma photons could have been produced by positron annihilation.

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