Particles & Antiparticles

Q1. A ____ is the antiparticle of the electron, having the same mass but ____ charge.

Fill In Blanks · 2 points

• · positron
• · opposite
• · greater
• · antiproton
• · equal
• · neutrino

Q2. Which of the following correctly pairs each particle with its antiparticle?

Multiple Choice · 1 point

• · Electron - antineutron, proton - positron
• · Electron - positron, proton - antiproton
• · Neutron - antineutrino, electron - antiproton
• · Proton - antineutron, neutrino - positron

Q3. How does the rest energy of an antiproton compare to that of a proton?

Multiple Choice · 1 point

• · It is double that of the proton
• · It is half that of the proton
• · It is equal to that of the proton
• · It depends on the speed of the antiproton

Q4. Which of the following correctly gives the charge of an antineutron?

Multiple Choice · 1 point

• · +1
• · -1
• · 0
• · +2

Q5. Which of the following statements about a particle and its antiparticle is always true?

Multiple Choice · 1 point

• · They have opposite masses and opposite charges
• · They have the same mass and the same charge
• · They have the same mass but opposite charges
• · They have different rest energies but the same charge

Q6. Which of the following is the antiparticle of the electron antineutrino?

Multiple Choice · 1 point

• · Positron
• · Antiproton
• · Electron neutrino
• · Antineutron

Q7. An antiproton has a rest energy of 938.3 MeV. What is the charge of an antiproton in SI units?

Multiple Choice · 1 point

• · 0 C
• · +1.6 × 10⁻¹⁹ C
• · -1.6 × 10⁻¹⁹ C
• · +3.2 × 10⁻¹⁹ C

Q8. Which of the following correctly describes the antineutron?

Multiple Choice · 1 point

• · Same mass as the neutron, charge of -1
• · Same mass as the neutron, charge of 0
• · Greater mass than the neutron, charge of 0
• · Same mass as the neutron, charge of +1

Q9. A proton has a rest energy of approximately 938.3 MeV. What is the minimum total photon energy required to produce a proton-antiproton pair?

Multiple Choice · 1 point

• · 938.3 MeV
• · 469.2 MeV
• · 1876.6 MeV
• · 3753.2 MeV

Q10. A proton-antiproton pair annihilate at rest. Each has a rest energy of 938.3 MeV. What is the energy of each photon produced?

Multiple Choice · 1 point

• · 1876.6 MeV
• · 469.2 MeV
• · 938.3 MeV
• · 3753.2 MeV

Q11. Which of the following correctly explains why a neutron and antineutron are considered distinct particles despite both having zero charge?

Multiple Choice · 1 point

• · They have different masses
• · They have different rest energies
• · They are composed of different combinations of quarks and antiquarks
• · They interact differently with the electromagnetic force

Q12. Which of the following is emitted alongside a positron in β⁺ decay?

Multiple Choice · 1 point

• · Electron antineutrino
• · Electron neutrino
• · Antiproton
• · Antineutron

Q13. The rest energy of an electron is 0.511 MeV. Which of the following correctly gives the rest energy of a positron?

Multiple Choice · 1 point

• · 0 MeV, since the positron has no rest mass
• · 1.022 MeV, double that of the electron
• · 0.511 MeV
• · 0.256 MeV, half that of the electron

Q14. Put the following particles in order from smallest to largest rest energy.

Ordering · 2 points

• 1. Electron neutrino (approximately 0 MeV)
• 2. Electron / positron (0.511 MeV)
• 3. Proton / antiproton (938.3 MeV)
• 4. Neutron / antineutron (939.6 MeV)

Q15. Put the following statements in order to explain what happens when a particle meets its antiparticle.

Ordering · 2 points

• 1. A particle and its antiparticle come into contact
• 2. Both particles are annihilated and cease to exist
• 3. Their combined rest energy is converted entirely into photon energy
• 4. Two photons are produced travelling in opposite directions to conserve momentum