Quantum Phenomena (Particles)

Question 1

Strong Nuclear Force:

Answer 1

Force that overcomes electrostatic force of repulsion between the protons in the nucleus and keeps the protons and neutrons together.
(0.5-3fm: At separations smaller than this, a repulsive force acts to prevent protons and neutrons from pushing into eachother).

Question 2

Strangeness:

Answer 2

Baryon, Meson, Lepton- 0 strangeness.

Kaon- 1 strangeness

Question 3

Particle X can decay to produce a neutron and positive pion as shown in this equation.
X → n + π+
Name Interaction (1 mark).
Explain your answer. (2 marks)

Answer 3

Answer 1: Weak interaction.
Answer 2: Strangeness of X is -1.
So reaction goes from -1 —->0 Strangeness.
This can only occur in weak interactions.

Question 4

Strange Quark Decay:

Answer 4

Strange quark (and antiquark) is unstable so decays into an up quark, an electron and an anti electron neutrino.

Question 5

Ionisation:

Answer 5

The removal of electrons from an atom.

Question 6

1)Under certain conditions a photon may be converted into an electron and a positron.
State the name of this process.

2)For the conversion to take place the photon has to have an energy equal to or greater
than a certain minimum energy.
Explain why there is a minimum energy. (2 marks)

3)Explain what happens to the excess energy when the photon energy is greater than the
minimum energy.
[1 mark]

Answer 6

1) Pair production.

2)

• energy of photon needs to provide at least the rest masses
• of the electron and positron

3) Utilised as kinetic energy in the positron and electron.

Question 7

State what is meant by the wave-particle duality of electrons (1 mark)

Answer 7

Electrons can have wavelike properties and particle like properties

Question 8

What property defines a hadron?

Answer 8

Affected by strong nuclear force (SNF).

Question 9

What is the quark structure of a baryon?

Answer 9

Particles composed of three quarks.

Question 10

What is the quark structure of a meson?

Answer 10

Particles composed of a quark and an antiquark

Question 11

State one similarity and one difference between a particle and its antiparticle.

Answer 11

Similarity: The same (rest) mass or rest energy

Difference: Opposite quantum states eg charge

Question 12

Quark structure of antiproton:

Answer 12

Antiup, antiup, antidown

Question 13

Reason for weak interaction being responsible for certain decays:

Answer 13

Strangeness not conserved

Question 14

State two differences between the exchange particles used by the weak interaction
and used by the electromagnetic force. (2 marks)

Answer 14

γ is massless y = PHOTON
γ has infinite range
γ does not carry charge
(1)(1) any two

Question 15

State what is meant by an antiparticle. (2 marks)

Answer 15

-All properties/quantum numbers (e.g. charge, strangeness)
are opposite (1)
-But the masses are the same (1)

Question 16

Where does the electron on the left-hand side of the equation come from IN an electron capture reaction? (1 mark)
And
Explain why this reaction has to produce a neutrino rather than an antineutrino. (1 mark)

Answer 16

• (Inner) shell (of atom)

- conservation of lepton number

Question 17

Exchange particle for electron capture:

Answer 17

W+ boson

Question 18

State what roles exchange particles can play in an interaction. (2 marks)

Answer 18

-Transfers energy
-Transfers momentum
-Transfers force
Any two

Question 19

State one difference between hadrons and leptons (1 mark)

Answer 19

-Hadrons experience the strong nuclear force

Question 20

Explain which fundamental interaction is responsible for the decay in
question 01.1. (2)

Answer 20

• Weak interaction (1st mark)

- BECAUSE change in quark composition (2nd mark)

Question 21

Strange particles

Answer 21

Strange particles as particles that are produced through the
strong interaction and decay through the weak interaction
(eg kaons).
Strangeness (symbol s) as a quantum number to reflect the
fact that strange particles are always created in pairs.
Conservation of strangeness in strong interactions.
Strangeness can change by 0, +1 or -1 in weak interactions.