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Physics > 2.3 Particles and radiation - Conservation laws & particle interactions > Flashcards

2.3 Particles and radiation - Conservation laws & particle interactions Flashcards

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1
Q

What are the 4 fundamental interactions or fundamental forces?

A
  • Gravity
  • electromagnetism
  • strong nuclear
  • weak nuclear
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2
Q

What are the ranges of the fundamental forces?

A
  • electromagnetic and gravitational intereactions have infinite range
  • weak force has a range of up to 10^-18
  • strong force has a range of up to 10^-15
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3
Q

What is the order of strength from strongest to weakest for the fundamental forces?

A
  • strong
  • electromagnetism
  • weak
  • gravitational
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4
Q

What are the properties of the fundamental forces?

A
  • gravitational only affects particles with mass
  • electromagnetic affect particles with charge
  • weak interaction affects all particles
  • strong interactions only effect hadrons
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5
Q

What is another word for exchange particles?

A

visual particles

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6
Q

Why must exchange particles exist?

A

when two particles interact
- there cannot be instantaneous action at a distance
- this means one particle needs to know that the other is there

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7
Q

How are virtual particles created?

A
  • two particles exert force on each other
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8
Q

What are virtual particles?

A
  • exist for a short time
  • carry the fundamental force between each particle
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9
Q

What is the electromagnetic force?

A

forces that only occur between charged particles

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10
Q

What is the exchange particle that carries the electromagnetic force?

A

virtual photon

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11
Q

What are the properties of the photon?

A
  • has no mass
  • has no charge
  • is its own antiparticle
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12
Q

When do electromagnetic interactions occur?

A

Whenever two charged particles interact with each other

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13
Q

Why are electromagnetic forces responsible for binding to atoms?

A

due to the attractive force between the negative electron and positive nucleus

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14
Q

What are the exchange particle of the strong nuclear forces interactions, and when are they used?

A
  • the pion - between nucleons
  • the gluon - between quarks
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15
Q

What are the weak interactions responsible for?

A

the radioactive decay of atoms

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16
Q

What is the exchange particles responsible for weak interactions?

A

W-
W+
Z0
bosons

17
Q

What occurs in Beta - decay and what is it an example of?

A
  • e.g. of weak interaction in action
  • a neutron turns into a proton emitting an electron and an anti-electron neutrino
  • The W- boson is the exchange particle in this interaction
18
Q

What occurs in beta plus decay?

A
  • proton turns into a neutron
  • emitting a positron and an electron neutrino
  • the W+ boson is the exchange particle in this interaction
19
Q

What occurs when electrons and protons area attracted to each other via the electromagnetic interaction?

A
  • they interact with each other, it is the weak interaction that facilitates the collision
20
Q

What is the electron capturer and electron - proton collisions decay equation?

A

proton + electron -> neutron + electron neutrino

21
Q

What is electron capture?

A
  • when an atomic electron is absorbed by a proton in the nucleus
  • resulting in the release of a neutron and a electron neutrino
  • the decay is mediated by the W+ boson
22
Q

What is electron-proton collisions?

A
  • when an electron collides with a proton
  • a neutron and electron neutrino are emitted
  • this decay is mediated by the W- boson
23
Q

What is a Feynman diagram?

A

a clear way of representing particle interactions in terms of their incoming and outgoing particles and exchange particles

24
Q

What are the rules of a Feynman diagram?

A
  • vertical axis represents time
  • horizontal axis represents space
  • gauge bosons are represented by a savvy or dashed lines or a helix
  • all other particles are represented by a wavy or dashed lines or a helix
  • all other particles are represented by straight lines
  • each line apart from neutral bosons can have an error with its direction forward in tie
  • the total charge, baryon number and lepton number must be conserved at each vertex
  • particle lines must not cross over
25
Q

How are exchanged particles represented in Feynman diagrams?

A
  • the weak interaction, W and Z bosons are represented by a wavy line
  • W+ and W- can have an error showing their direction or must be slanted upwards, meaning that they are forward in time
  • pions are represented by a wavy or dashed line
  • photons are represented by a wavy line
  • gluons are represented by a helix
26
Q

How is the sign of the W particle determines?

A
  • dependent on the other particles involved in the decay
  • because charge must be conserved at each vertex, if a neutron turns into a proton the W- carries away a negative charge from the neutral neutron, leaving a positive charge of the proton
  • negative charge is the carried to the vertex with the electron and anti-neutrino
27
Q

What is the quark transformation in beta decay?

A
  • occurs due to weak interaction between the quarks
  • when a neutron turns into a proton emitting an electron and anti-electron neutrino
  • this happens by turning a down quark into an up quark
  • the W- boson carries the negative charge of the down quark providing the negative charge for the electron and anti - neutrino
28
Q

What is the quark composition in Beta plus decay?

A
  • when a proton turns into a neutron emitting a positron and an electron neutrino
  • proton turns into a neutron because an up quark turns into a down quark
  • W+ boson carries the positive charge of the up quark providing a positive charge for the positron and neutrino
29
Q

In particle interactions, what conservation laws must be obeyed?

A
  • charge
  • baryon number
  • lepton number
  • strangeness
  • energy
  • momentum
30
Q

What is the exception in conservation laws?

A

Strangeness does not need to be conserved in weak interactions

Physics (18 decks)

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