# Worksheet: Subatomic Particles

Q1:

Identify the missing particle in the reaction .

• A
• B
• C
• D
• E

Q2:

A neutral pion has a rest mass of 135.0 MeV. Assuming conservation of momentum, what is the energy of each ray produced in the decay of a neutral pion at rest. The reaction produces two equal energy photons.

Q3:

Consider the following decays of unstable subatomic particles: Which of these decays cannot occur because the law of conservation of lepton number would be violated?

• A
• B
• C
• D
• E

Q4:

An electron has a rest mass of 0.511 MeV. How much energy is released when an electron and a positron at rest annihilate each other?

Q5:

Identify the missing particle in the reaction .

• A
• B
• C
• D
• E

Q6:

Consider the following decays of unstable subatomic particles: Which of these decays cannot occur because the law of conservation of lepton number would be violated?

• A
• B
• C
• D
• E

Q7:

An electron has a rest mass of 0.511 MeV. When both an electron and a positron are at rest, they can annihilate each other according to the reaction . The energies of the photons produced in the reaction are equal to each other, as are the photonβs momenta and their frequencies.

What is the energy of one of the photons?

• A 0.383 MeV/c2
• B 0.475 MeV/c2
• C 0.362 MeV/c2
• D 0.511 MeV/c2
• E 0.256 MeV/c2

What is the momentum of one of the photons?

• A kgβm/s
• B kgβm/s
• C kgβm/s
• D kgβm/s
• E kgβm/s

What is the frequency of one of the photons?

• A Hz
• B Hz
• C Hz
• D Hz
• E Hz

Q8:

Identify the missing particle in the reaction .

• A
• B
• C
• D
• E

Q9:

Identify the missing particle in the reaction .

• A
• B
• C
• D
• E

Q10:

The decays of unstable subatomic particles can be described using equations: Which of the decays shown cannot occur because the law of conservation of lepton number would be violated?

• A
• B
• C
• D
• E

Q11:

A negative pion has a rest mass of 139.6 MeV. The primary decay mode for negative pions is . A muon has a rest mass of 105.7 MeV, while a neutrino has negligible rest mass and a momentum . A pion that is at rest undergoes a primary mode decay .

How much energy is released in this decay?

How much energy does the muon take from the reaction?

How much energy does the neutrino take from the reaction?

Q12:

Identify the missing particle in the reaction .

• A
• B
• C
• D
• E