P1: Matter and Radiation Flashcards

Decay, categories of subatomic particles, interactions, radioactivity

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1
Q

What is electron capture?

A

When a proton from a proton-rich nucleus interacts with an inner shell electron through the weak interaction, turning into a neutron using a W-boson.
The electron is turned into a neutrino.
(can also happen when an electron and proton collide at high speeds).

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2
Q

The weak force

A
  • A force weaker than the strong force, enacted by the W-boson.
  • It occurs in the weak interaction and in beta decay.
  • Affects all types of particles, when quark structure changes
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3
Q

Characteristics of a W+/W- boson

A
  • have a non-zero mass
  • have a range of no more that 0.001fm (very short with a very short half life too)
  • can be positively or negatively charged
  • are leptons
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4
Q

W bosons in beta decay

What does a W+/W- boson do?

A

A W- boson decays into a B- particle and an antineutrino.
A W+ boson decays into a B+ particle and a neutrino.

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5
Q

The 4 fundamental forces

+ a bit about each one

A

Electromagnetic: the force between any two charged objects, exerted by the virtual photon.
Strong Nuclear: the force holding the nucleus together, enacted by the gluon/pion.
Weak: force felt by any particle, exerted by W bosons.
Gravitational: enacted by the gravitron (in theory) on any particle with mass.

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6
Q

What must be conserved during any particle interaction?

A
  • Lepton number
  • Baryon number
  • Charge
  • Strangeness (but not important for weak interactions)
  • Energy
  • Momentum
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7
Q

Specific charge

A

= charge / mass (meaured in C/kg)

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8
Q

About the strong force… (Give at least 1 point out of 4)

A
  • Its range is no more than about 3-4 fm (x10^-15 m) which is about the same as the diameter of a small nucleus
  • It has the same effect between 2 protons as it does between a proton and a neutron or between 2 neutrons
  • At separations less than 0.5fm, it is repulsive, in order to stop nuclear components from colliding with each other
  • It counteracts the electrostatic repulsion between protons
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9
Q

Specific Charge of a Proton?

A

charge/mass = 9.58 x 10^7

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10
Q

State a use of radioactive isotopes

A

Carbon Dating: the proportion of carbon-14 in a material tells us it approximate age.

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11
Q

What makes a nucleus unstable?

A

Having too many protons and/or neutrons.

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12
Q

What kind of decay takes place when an atom has too many nucleons?

A

Alpha decay (-2 protons -2 neutrons from the nucleus)

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13
Q

Decaying when there are too many neutrons in an atom is..?

And say what change occurs (+1)

A

Beta decay (neutron decays to a proton; udd into uud) by the weak interaction

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14
Q

How was the neutrino’s existence hypothesised?

A

During beta decay a particle with 0 charge and negligible mass must have been emitted to account for the energy lost.

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15
Q

Antiparticles

A

Are particles with the same rest energy and mass but with other qualities completely opposite to each other.
Every particle has one.

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16
Q

When does annihilation take place.

A

When a particle and its antiparticle meet.

17
Q

Describe the process of annihilation.

A

The mass of both is converted into energy in the form of 2 gamma ray photons which travel off in opposite directions, conserving momentum.

18
Q

Describe Pair Production.

A

When a gamma photon is converted into a particle-antiparticle pair.

19
Q

How to find the minimum energy of a photon required for pair production of any two particles?

A

2 x (the rest energy of that particle) measured in MeV

20
Q

What do Kaons decay into?

A

Pions

20
Q

Strange particles are produced by..?

A

The strong interaction and decay by the weak interaction.

20
Q

What do muons decay into?

A

An electron and two types of neutrino

20
Q

Which particles does the strong force affect?

A

Hadrons (not leptons)

21
Q

What is Electromagnetic Repulsion?

You need to know the diagram for this.

A

When two particles with equal charges get close to each other and repel. Enacted by the virtual photon.