2.1 Particles Flashcards

1
Q

What is meant by Specific Charge?

A

The Charge to Mass ratio:
Specific Charge = charge/mass
Units: C/kg

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2
Q

What is Nucleon?

A

A constituent of the nucleus : proton or neutron

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3
Q

What is an isotope?

A

A version of an element with the same number of protons ,but different numbers of neutrons

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4
Q

State a use of radioactive isotopes.

A

Carbon dating : the proportion of carbon-14 in a material can be used to estimate its age

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5
Q

What is the strong nuclear?

A

the fundamental force that keeps the nucleus stable by counteracting the electrostatic repulsive force between protons

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6
Q

Describe the range of the strong force.

A

1) repulsive up to 0.5fm
2) attractive from 0.5-3fm
3) negligible past 3fm

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7
Q

What makes a nucleus unstable?

A

Nuclei with either too many of either protons or neutrons

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8
Q

How do nuclei with too may nucleons decay?

A

Alpha decay (emissions of helium nucleus - 2 protons and 2 neutrons)

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9
Q

How do nuclei with too many neutrons decay?

A

Beta minus decay in which the neutron decays into a proton b the weak interaction (quark character has changed from udd to uud )

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10
Q

How was the existence of the neutrino hypothesised?

A

the energy of the particles after beta decay was lower than before, a particle with 0 charge (to conserve charge) and negligible mass has to carry away the excess energy , this is the neutrino

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11
Q

What is meant by beta minus decay?

A

When a neutron turns into proton , the atom releases an electron and an anti-electron neutrino

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12
Q

What is an anti particle?

A

For each particle there is an anti particle , they have the same rest energy and mass , but everything else is opposite so they have the opposite charge

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13
Q

What occurs when a particle and an anti-particle meet?

A

Annihilation:
The mass of the particle and anti-particle is converted into energy in the form of 2 gamma ray photons going in opposite directions to conserve momentum

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14
Q

What is pair production?

A

A gamma ray photon is converted into a particle anti-particle pair

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15
Q

What is the minimum energy of a photon needed to make a proton antiproton pair?

A

2x proton rest energy

Unit:eV

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16
Q

Name the 4 fundamental forces?

A

1) Gravity
2) Electromagnetic
3) Weak nuclear
4) Strong nuclear

17
Q

The virtual photon is the exchange particle between what force?

A

The electromagnetic force

18
Q

What type of particles are affected by the strong nuclear force?

19
Q

What is the exchange particle of the weak nuclear force?

A

The W boson (W+ or W-)

20
Q

What does the electromagnetic force act on?

A

Any particle with a charge

21
Q

When does the weak interaction occur?

A

When the quark character changes (when a quark turns into another quark), it affects all kinds of particles

22
Q

Which properties must be conserved in particle interactions?

A

1) Energy
2) Charge
3) Baryon number
4) Lepton number
5) Momentum
6) Strangeness (only for strong interactions)

23
Q

What is a hadron?

A

Both baryons and mesons are hadrons , they consist of 2 or more quarks held together by the strong nuclear force

24
Q

What are the classes of hadrons?

A

1) Baryons (3 quarks)

2) Mesons (1 quark 1 anti-quark)

25
The pion can be the exchange particle of what force?
The strong nuclear force
26
What particle does a kaon decay into?
A kaon decays into a pion
27
What is significant about a proton?
1) Only stable baryon | 2) All baryons decay into protons
28
What are some examples of leptons ?
1) Electron 2) Muon 3) Neutrino 4) all antiparticles of the above
29
What does a Muon decay into?
An electron
30
What is the strangeness value of a strange quark?
-1
31
Is strangeness conserved in the weak interaction?
No ,strangeness is only conserved in the strong nuclear interaction , in the weak interaction it can change by 0,-1 or +1
32
Electron capture
A proton captures an inner shell electron and becomes a neutron and an electron neutrino with the W+ boson as the exchange particle
33
Electron and proton collision
Electron and proton collide and a W- boson particle is exchanged. Electron turns into an electron neutrino and the proton becomes a neutron