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Flashcards in G485 - Nuclear Physics Deck (68)
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1
Q

Describe Rutherford’s alpha particle scattering experiment

A

A beam of alpha particles (helium nuclei) was directed at a thin sheet of gold leaf
The leaf was surrounded by a ring of detectors to pick up where the alpha particles went after passing through the gold leaf

2
Q

What were the observations from Rutherford’s alpha particle scattering experiment?

A

Most alpha particles passed straight through the gold leaf with little or no deflection
A few alpha particles were deflected through large angles

3
Q

What conclusions can be drawn from Rutherford’s alpha particle scattering experiment?

A

Atoms are mostly empty space
Mass is concentrated at a single point, the nucleus
The nucleus is positively charged as it repelled the positively charged alpha particles

4
Q

Nucleus Diameter

A

10^-15

5
Q

Atom Diameter

A

10^-10

6
Q

Relative mass of a neutron

A

1

7
Q

Relative mass of a proton

A

1

8
Q

Relative mass of an electron

A

1/1840

9
Q

Nucleon / Mass Number Definition

A

The number of nucleons in the nucleus

10
Q

Proton / Atomic Number Definition

A

The number of protons in the nucleus

11
Q

Isotope Definition

A

Different form of the same element containing the same number of protons in the nucleus but a different number of neutrons

12
Q

What quantities are conserved in nuclear decay?

A
charge
momentum
lepton number 
baryon number
mass / energy
spin
13
Q

List the four forces in the universe from strongest to weakest

A

Strong Nuclear Force
Electromagnetic Force
Weak Nuclear Force
Gravitational Force

14
Q

Properties of the Strong Nuclear Force

A

Short ranging
Attractive at longer distances
Repulsive at very short distances
Acts on quarks

15
Q

Properties of the Electromagnetic Force

A
Only acts between objects with charge
Attractive between opposite charges
Repulsive between like charges
Long ranging
Obeys the inverse square law
16
Q

Properties of the Weak Nuclear Force

A

Can effect any particle

Governs nuclear decay

17
Q

Properties of the Gravitational Force

A

Acts between objects with mass
Always attractive
Long ranging
Obeys the inverse square law

18
Q

Fundamental Particle Definition

A

A particle which cannot be broken down any further

19
Q

What is the exchange particle for the Strong Nuclear Force?

A

gluon

20
Q

What is the exchange particle for the Electromagnetic Force?

A

photon

21
Q

What is the exchange particle for the Weak Nuclear Force?

A

W and Z bosons

22
Q

What is the exchange particle for the Gravitational Force?

A

graviton

23
Q

Hadron Definition

A

a particle which is made up of quarks

24
Q

Baryon Definition

A

a hadron which is made up of three quarks

25
Q

Meson Definition

A

a hadron which is made up of a quark and an anitquark

26
Q

Lepton Definition

A

fundamental particles which are not effected by the strong nuclear force

27
Q

Examples of Mesons

A

pion

kaon

28
Q

Examples of Baryons

A
proton
neutron
lambda
sigma
omega
29
Q

Examples of Leptons

A

electron
muon
tau
neutrino

30
Q

Antimatter Defintion

A

the opposite of matter in every way

31
Q

What happens when a particle collides with its antiparticle?

A

They annihilate

The equivalent of their mass is released as two photons in opposite directions

32
Q

What is a β- particle?

A

electron

33
Q

What is a β+ particle?

A

positron

34
Q

Beta Minus Decay

A

neutron -> proton + electron + antielectronneutrino

ExchangeParticle = W- Boson

35
Q

Beta Plus Decay

A

proton -> neutron + positron + electronneutrino

ExchangeParticle = W+ Boson

36
Q

Alpha Decay

A

(X,Y)^A -> (X-4,Y-2)B + (4,2)He

37
Q

Gamma Decay

A

(X,Y)A -> (X,Y)A + gammaphoton

38
Q

What is the quark composition of a proton?

A

uud

39
Q

What is the quark composition of a neutron?

A

udd

40
Q

What are the 6 types of quark?

A
up
down
strange
top
bottom
charm
41
Q

Binding Energy Definition

A

minimum energy required to separate all of the nucleons in a nucleus

42
Q

Binding Energy per Nucleon Definition

A

energy required to remove a nucleon from the nucleus of an atom

43
Q

Mass Defect Definition

A

during nuclear decay the mass of particles before the decay is always greater than the total mass after the decay, the difference in mass is the mass defect and is equivalent to the energy released in the decay, E=mc²

44
Q

What is the most stable nucleus?

A

Iron, has the greatest binding energy per nucleon
Nuclei smaller than iron fuse to make iron which releases energy
Elements larger than iron fission to release energy

45
Q

Describe Nuclear Fission

A

U-235 nucleus absorbs a slow moving neutron
The new nucleus is very unstable, it decays to form two daughter nuclei which are roughly equal in size
Three neutrons are also released as well as energy

46
Q

Describe how a chain reaction can start

A

When an unstable nucleus decays it releases three neutrons which can go on to cause a further three nuclei to decay and release another three neutrons each
Reaction rate will increase exponentially if uncontrolled

47
Q

Describe the role of fuel rods in a nuclear reactor

A

Contain unstable nuclei which will decay when bombarded with slow moving neutrons

48
Q

Spontaneous Fission

A

some radioactive isotopes contain nuclei that are highly unstable
at some point they will naturally decay

49
Q

Induced Fission

A

fisson can be induced by bombarding atoms with neutroms

50
Q

Describe the role of control rods in a nuclear reactor

A

Control rods can be lowered to absorb neutrons and slow down the rate of the chain reaction
Control rods can be raised so that more neutrons can collide with nuclei and cause decay to increase the reaction rate

51
Q

Describe the role of the moderator in a nuclear reactor

A

the moderator (made of graphite) slows down neutrons so the they can be absorbed by the uranium nuclei
this process generates heat
coolant absorbs heat

52
Q

Advantages of Nuclear Fission to Produce Energy

A

high energy yield
efficient
doesn’t produce greenhouse gases

53
Q

Disadvantages of Nuclear Fission to Produce Energy

A

radioactive waste
nuclear meltdown
radiation
initially very expensive and expensive to decommission

54
Q

Why is nuclear fusion possible inside stars?

A

Extremely high pressure and temperature

55
Q

Radioactive Decay

A

spontaneous and random

it is impossible to predict when an individual nucleus will decay

56
Q

Alpha Radiation

Nature

A

helium nucleus (2 protons, 2 neutrons)

57
Q

Beta Radiation

Nature

A

electron

58
Q

Gamma Radiation

Nature

A

electromagnetic radiation

59
Q

Alpha Radiation

Range

A

short

60
Q

Beta Radiation

Range

A

medium

61
Q

Gamma Radiation

Range

A

long

62
Q

Alpha Radiation

Penetration

A

absorbed by thin paper

63
Q

Beta Radiation

Penetration

A

absorbed by a few mm of aluminium

64
Q

Gamma Radiation

Penetration

A

absorbed by a few cm of lead

65
Q

Activity Definition

A

A, the number of radioactive decays per unit time (Bq)

66
Q

Decay Constant Definition

A

λ, the probability that an individual nucleus will decay n a unit time (s^-1)

67
Q

Half Life Definition

A

the time taken for the number of radioactive nuclei to decrease by half

68
Q

Radiocarbon Dating

A

Living things take in carbon, after death this stops, carbon-14 in the organism decays to carbon-12
The ratio of carbon-14 to carbon-12 in the sample can be determined
Compared with the ratio of carbon-14 to carbon-12 in a loving organism
Age of sample found using X = X0e^(-λt)