3.2.1.7 Applications of Conservation Laws

Question 1

Which 6 things are conserved in interactions?

Answer 1

Charge
Baryon Number
Lepton Number
Strangeness
Energy
Momentum

Question 2

What does the conservation of charge state?

Answer 2

In all interactions, charge must be conserved.

So the sum of charge before = the sum of the charges after.

Question 3

What does the conservation of baryon number state?

Answer 3

In all interactions, baryon number must be conserved.

Question 4

What does the conservation of lepton number state?

Answer 4

In all interactions, lepton number must be conserved.

Question 5

What does the conservation of strangeness state?

Answer 5

In all interactions involving the strong force, strangeness must be conserved. In weak interactions, strangeness can be conserved, or can change by +/- 1.

Question 6

Give an example of how charge is conserved in pair production.

Answer 6

In pair production, a photon with enough energy can produce an electron-positron pair. It could not produce just one or the other, because the total charge before would not be equal to the total charge after.

Question 7

Give an example of how charge is conserved in a neutral neutron decay.

Answer 7

When a neutral neutron decays into a proton, a particle with a negative charge must also be produce to cancel out the charge of the proton.

Question 8

Which two lepton numbers must be counted separately for conservation?

Answer 8

Muon lepton number and electron lepton number must be counted seperately.