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Physics A-Level > Chapter 1: Particles And Radiation > Flashcards

Chapter 1: Particles And Radiation Flashcards

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1
Q

Describe the structure of an atom.

A

There is a nucleus comprised of neutrons and protons which electrons orbit. Most of an atom is empty space.

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2
Q

What is the relative charge of each particle in the atom.

A

Proton = 1+
Electron = 1-
Neutron = 0

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3
Q

Give the relative masses of each of the particles in the atom.

A

Proton = 1
Electron = 1/2000
Neutron = 1

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4
Q

What is the proton number of an atom?

A

The number of protons in the nucleus. Represented by the letter Z.

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5
Q

What is the nucleon number of an atom?

A

The total number of protons and neutrons in an atom. Represented by the letter A.

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6
Q

What is specific mass and what units is it measured in?

A

The charge of a particle divided by its mass. It is measured in C kg^-1

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7
Q

What are isotopes?

A

Atoms with the same number of protons but a different number of neutrons.

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8
Q

Give an example of how isotopic data can be used.

A

To calculate the age of organic matter. This is done by calculating the percentage of carbon which is radioactive carbon-14 present in the object being studied.

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9
Q

What are the two largest forces acting on the particles in a nucleus?

A

The electromagnetic force (between protons) and the strong nuclear force.

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10
Q

What is the range of repulsion of the strong nuclear force?

A

Between 0 and 0.5 fm.

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11
Q

What is the range of attraction of the strong nuclear force?

A

Between 0.5 and 3 fm.

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12
Q

Explain how we know there must be a strong nuclear force.

A

The electrostatic repulsion is much greater than the gravitational attraction. Without another force, the strong nuclear force, the nucleus would fly apart.

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13
Q

What is a ß- particle also known as?

A

A electron

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14
Q

Why does a nucleus undergo nuclear decay?

A

Because the forces in the nucleus only have a range of a few femtometres, so they struggle to hold larger nuclei together. This makes the nucleus unstable.

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15
Q

How do the nucleon and proton numbers of an atom change in alpha decay?

A

Nucleon number decreases by 4.
Proton number decreases by 2.

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16
Q

Give two ways of demonstrating the range of alpha particles.

A
  1. Using a cloud chamber to observe tracks left by alpha particles.
  2. Using a Geiger counter or spark counter to measure the amount of ionising radiation at different distances from an alpha source.
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17
Q

What particles are emitted during beta-minus decay?

A

An electron and an antineutrino.

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18
Q

What type of nuclei will decay by beta-minus decay?

A

Neutron rich nuclei.

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19
Q

Describe the changes in the nucleus of an atom when it undergoes beta-minus decay.

A

A neutron turns into a proton, so the nucleon number stays the same and the proton number increases by 1.

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20
Q

Explain how the neutrino was hypothesised as a result of beta decay.

A

It originally appeared as though energy was being lost in beta decay. A new particle was hypothesised in order for energy to remain conserved. This particle had to be neutral and was named the ‘neutrino’.

21
Q

What is a photon?

A

A ‘packet’ of EM radiation.

22
Q

What equation would you use to calculate the energy of a photon from its wavelength?

A

E = hc/λ

23
Q

How is an antiparticle different and the same from its corresponding particle?

A

It has the opposite charge but the same mass and rest energy.

24
Q

What is the relative charge of the antineutrino?

A

0

25
Q

Describe the process of pair production.

A

Energy can be converted into mass and produce particles, if there is enough energy. The mass is always produced in a particle-antiparticle pair.

26
Q

What is produced in the annihilation of matter and antimatter?

A

Two gamma ray photons.

27
Q

What type of particle feels the strong nuclear force?

A

Hadrons

28
Q

What particles is believed to be the only stable baryon?

A

Proton

29
Q

Write down the baryon number of:
1. Electron
2. Antineutron
3. Kaon

A
  1. 0
  2. -1
  3. 0
30
Q

What particles are produced when a neutron decays into a proton?

A

An electron and antineutrino (and a proton).

31
Q

Explain what cosmic ray showers are.

A

High-energy particles produced as a result of radiation from space interacting with molecules in the atmosphere.

32
Q

What is the relative charge of an antimuon?

A

+1

33
Q

In what type of interaction are strange particles produced in pairs?

A

Strong interaction

34
Q

What special property do strange particles have?

A

Strange particles are always produced in pairs.

35
Q

In what type of interaction do strange particles decay?

A

The weak interaction

36
Q

In which interaction is strangeness not conserved?
By how much can strangeness change in this type of interaction?

A

The weak interaction. Strangeness can be changed by -1, 0 or +1.

37
Q

What properties are always conserved in particle interactions?

A

Charge, baryon number, lepton number, mass, energy, momentum.

38
Q

Name 3 quarks.

A

Up, down and strange

39
Q

What is the baryon number of a quark?

A

-1

40
Q

What is the quark composition of a meson?

A

1 quark and 1 antiquark

41
Q

Why can you not have a quark on its own?

A

The energy used to remove a quark from a hadron creates a quark-antiquark pair. It’s called quark confinement.

42
Q

What sort of interaction can change a quark’s character? Name and describe an interaction in which this happens.

A

The weak interaction. In ß- decay, a neutron decays to a proton so a down quark changes to an up quark.

43
Q

What is an exchange particle?

A

A virtual particle that lets a force act between two particles in an interaction.

44
Q

Name the electromagnetic force exchange particle.

A

Virtual photon

45
Q

Name two exchange particles of the weak interaction.

A

W+ and W- bosons

46
Q

What do the straight lines on particle interaction diagrams represent?

A

Particles

47
Q

Why would a nucleus undergo electron capture?

A

Because it is proton rich.

48
Q

What is the difference between electron capture and electron-proton collisions?

A

In electron capture, a proton in a nucleus captures an electron from the atom, turning into a neutron and emitting a neutrino. In an electron-proton collision, a free electron collides with a free proton, producing a neutron and a neutrino.

49
Q

What are the exchange particle for electron capture, and what particles are produced?

A

The W+ boson is the exchange particle and a neutron and an electron neutron are produced.

Physics A-Level (7 decks)

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