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LAET A-level OCR Physics A 2023 > Nuclear Physics and Particles > Flashcards

Nuclear Physics and Particles Flashcards

1
Q

How do you calculate the mass defect of a nucleus?

A

The mass defect of a nucleus is defined as the difference between the mass of the separated nucleons and the combined mass of the nucleus.

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2
Q

What is nuclear fusion?

A

is the combining of the two light nuclei to produce a heavier nucleus.

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3
Q

What is nuclear fission?

A

is the disintegration of a heavy nucleus into two lighter nuclei of approximately equal masses.

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4
Q

Define radioactive decay

A

is the spontaneous decaying of the nucleus of an atom which results in the emission of particles.

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5
Q

What is background radiation?

A

Ionizing radiation emitted from a variety of natural and artificial radiation sources. It should be constant isotropic and uniform

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6
Q

What is the activity of a sample?

A

The activity of a radioactive substance is defined as the average number of atoms disintegrating per unit time.

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6
Q

What is the activity of a sample?

A

The activity of a radioactive substance is defined as the average number of atoms decaying per unit time.

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7
Q

What is the decay constant?

A

The decay constant λ of a nucleus is defined as its probability of decay per unit time

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8
Q

Define half-life

A

Half-life is defined as the time taken for half the original number of radioactive nuclei to decay

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9
Q

Explain the role of the moderator

A

The moderator slows down fast neutrons making them thermal neutrons to make fission more likely to happen.

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10
Q

What are possible materials for the moderator?

A

Water, Graphite.

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11
Q

What is the role of the control rods?

A

Reduce the number of neutron in the fission reactor

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12
Q

What are possible material for control rods?

A

Boron and Cadmium

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13
Q

Define the Nuclear Binding Energy

A

Nuclear binding energy is the energy required to disassemble a nucleus into the free, unbound neutrons and protons it is composed of

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14
Q

proton number

A

number of protons in the nucleus of an atom (a.k.a. atomic number)

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15
Q

nucleon number

A

number of neutrons and protons in the nucleus of an atom (a.k.a. mass number)

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16
Q

What are Isotopes

A

Different forms of the same element or nuclei having the same number of protons with different
numbers of neutrons

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17
Q

Which group of particles are subject to the weak nuclear force but not the strong nuclear force

A

Leptons

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18
Q

What is the quark composition of a meson?

A

A quark and an antiquark.

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19
Q

Which force do Hadrons decay by?

A

The weak nuclear force.

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20
Q

What is the quark composition of a Baryon

A

Three quarks

21
Q

What is a neutrino?

A

A lepton with no charge and a tiny mass.

22
Q

Why doesn’t a neutrino experience the electromagnetic force?

A

They have no charge.

23
Q

What is the quark composition of a neutron?

A

up down down (udd)

24
Q

What is the quark composition of a proton?

A

up up down (uud)

25
Q

What is the quark composition of an anti-baryon?

A

Three antiquarks

26
Q

Name the two types of hadron.

A

baryons and mesons

27
Q

What force hold quarks together in hadrons?

A

The strong nuclear force.

28
Q

What is the family of particles that are subject to both the strong and weak nuclear force?

A

Hadrons

29
Q

What type of particle are nucleons?

A

Baryons

30
Q

How does a proton compare to an antiproton?

A

he have the same mass but opposite charge.

31
Q

How does an electron compare to a positron?

A

The have the same mass but opposite charge.

32
Q

What is the antiparticle of the electron?

A

Positron.

33
Q

Describe beta minus decay.

A

A neutron in an unstable nucleus decays into a proton, electron and electron antineutrino.

34
Q

Describe beta plus decay.

A

A proton in an unstable nucleus decays into a neutron, positron and an electron neutrino.

35
Q

What quark transformation occurs during beta minus decay?

A

A down quark (in a neutron) turns into an up quark (in a proton)

36
Q

What quark transformation occurs during beta plus decay

A

An up quark (in a proton) turns into an down quark (in a neutron)

37
Q

What is the maximum range of the strong nuclear force?

A

~3fm

38
Q

Below what distance is the strong nuclear force repulsive?

A

0.5fm

39
Q

How did Rutherford estimate the maximum radius of the nucleus?

A

He equated the KE of the alpha particle to the electric potential energy at closest approach to the nucleus.

40
Q

What material was used as a target in Rutherford’s scattering experiment?

A

Gold foil, a few atoms thick

41
Q

What was measured in Rutherford’s scattering experiment?

A

The angle of deflection of the alpha particles.

42
Q

What happened to most of the alpha particles in Rutherford’s scattering experiment?

A

They passed straight through the foil (with very little scattering).

43
Q

What proportion of alpha particles were scattered in Rutherford’s scattering experiment?

A

Around 1 in 2000

44
Q

What proportion of alpha particles were deflected by more than 90° in Rutherford’s scattering experiment?

A

Around 1 in 10,000

45
Q

What was concluded due to most of the alpha particles passing straight through the gold foil Rutherford’s scattering experiment?

A

Most of the atom is empty space with most of the mass concentrated in a small nucleus.

46
Q

What was concluded due to some alpha particles being scattered in Rutherford’s scattering experiment?

A

The nucleus is positively charged.

47
Q

How did Rutherford estimate the maximum radius of the nucleus?

A

He equated the KE of the alpha particle to the electric potential energy at closest approach to the nucleus.

48
Q

How has the radius of the nucleus been measured?

A

By the diffraction of fast moving electron.

49
Q

What is R in R = r₀A^(1/3)?

A

The radius of the nucleus.

50
Q

What is r₀ in R = r₀A^(1/3) roughly equivalent to?

A

The radius of a proton.

51
Q

What is A in R = r₀A^(1/3)

A

Nucleon number.

LAET A-level OCR Physics A 2023 (15 decks)

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