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AQA A Level Physics Paper 2 Topics > Nulcear Physics > Flashcards

Nulcear Physics Flashcards

(76 cards)

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1
Q

What does symbol A represent

A

Mass number

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2
Q

What does symbol Z represent

A

Atomic number

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3
Q

What does symbol X represent

A

The element

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4
Q

Describe John Dalton’s model of the atom

A

Atoms are tiny solid spheres

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5
Q

Describe JJ Thompson’s model of the atom

A

Plum pudding model - atom are spheres of positive charge will negative electrons stuck in it

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6
Q

Describe Rutherford’s alpha scattering experiment

A

Fire alpha particles at a thin piece of gold foil

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7
Q

Why does the gold foil have to be thin for the alpha scattering experiment

A

So there’s only a 1-1 interaction

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8
Q

What’s conclusions were made from the alpha scattering experiment

A
  1. Atom is mostly empty space as most alpha particles went straight through
  2. Nucleus has a large positive charge as some particles were deflected by a large angle
  3. Mass is concentrated in the nucleus as some particles deflected more than 90 degrees
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9
Q

Why can electron diffraction be used to estimate nuclear radius

A

Electrons don’t interact with the strong nuclear force so its an accurate method

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10
Q

Why can electron beams be diffracted

A

They show wave-particle duality

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11
Q

What two equations can be used to find the radius of a nucleus

A
  • use wavelength = hc/E to find wavelength
  • use R = 1.22wavelength/ 2sinx to find radius
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12
Q

How does a diffraction pattern form

A

A high energy electron beam is directed onto a film

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13
Q

What is the average radius of a nucleus

A

1 x 10^15 m

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14
Q

What is the relationship between intensity of maxima and angle of diffraction

A

Intensity of maxima decreases as angle of diffraction increases

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15
Q

What shape is the angle of diffraction curve

A

Symmetric bell shaped curve

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16
Q

What is the relationship between nuclear radius and nucleon number

A

Nuclear radius is proportional to the cube root of the nucleon number

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17
Q

What is the equation linking nuclear radius and nucleon number

A

R = RoA^1/3
Where Ro is a constant and A is nucleon number

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18
Q

State the ration between nuclear radius and nucleon number

A

R1/R2 = A1^1/3 / A2^ 1/3

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19
Q

What is the equation to find the density of a nucleus

A

3m(nucleon number) / 4 pi Ro^3

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20
Q

What type nuclei decay

A

Unstable nuclei

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21
Q

What are 4 sources of background radiation

A
  • cosmic rays
  • radon gas
  • buildings
  • man-made radiation
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22
Q

What direction does a gamma source emit radiation

A

In all directions

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23
Q

What is the relationship of intensity vs distance from gamma source

A

Inverse square law

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24
Q

Define decay constant

A

The probability of a nucleus decaying per unit time

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25
Define activity
The number of nuclei that decay per second
26
What is activity proportional to
The size of the sample
27
What is the relationship between the value of decay constant and the rate of decay
The bigger the value of the gamma constant, the faster the rate of decay
28
What is the equation for activity
A = decay constant x number of atoms
29
What links activity and number of atoms What is the equation for this
Activity is the rate of change of N N/t = -A x decay constant
30
How does the number of undecayed particles change (graph wise)
Number of undecayed particles decreases exponentially
31
What graph has gradient -decay constant
Ln (No) against t, where No is number of radioactive atoms
32
What is the gradient of ln (No) against t
- decay constant
33
What is the equation for half life
T 1/2 = ln2/decay constant
34
What does the number of unstable nuclei remaining depend on
The number originally present, No
35
What is the equation for number of nuclei remaining
N = No e^ -t(decay constant)
36
A = Ao e^ -t(decay constant)
37
What are 3 advantages of nuclear fuel
- doesn’t release CO2 - can adjust power output - uranium is a very abundant element
38
What is a problem with nuclear waste
Transporting it to sites to be buried
39
What equation is used when finding the original mass of element a number of years ago
N = N0 e^-yt
40
Suggest 2 uses of different half lives
1 - radioactive dating of objects 2 - medical diagnosis
41
Describe radioactive dating of objects
Living plants absorb CO2 for photosynthesis which includes radioactive carbon-14 When plants die, activity of carbon-14 falls Date by finding current amount of carbon-14, knowing half-life
42
Describe using radioactivity for medical diagnosis
Gamma sources are used as medical tracers
43
What nuclei has alpha emission
Heavy nuclei
44
What nuclei has B- decay
Neutron - rich nuclei ; neutron changes into a proton
45
What nuclei emit gamma radiation
Nuclei with too much energy
46
When is gamma radiation usually emitted from nuclei
After alpha/beta decay as nucleus is excited and has excess energy
47
What is conserved in every nuclear reaction
Energy, momentum, charge and nucleon number
48
When is alpha emission likely (on graph)
Z > 60
49
What are 3 key coordinates on nuclear stability graph
(20,20), (60,60), (90,140)
50
Why does stable nucleus have exponential line on N-Z graph
Repulsive force becomes greater than strong nuclear force so neutrons needed to decrease distance between protons
51
Describe nuclear fission
The splitting of a large nucleus into 2 daughter nuclei
52
What does nuclear fission occur in
Large, unstable nuclei
53
Why is energy released in fission
The 2 daughter nuclei have a higher binding energy per nucleon than the larger unstable nucleus
54
What type of reaction is induced fission
A chain reaction
55
What fuel is used for induced fission
Uranium - 235
56
Define critical mass
The minimum mass of fuel required to maintain a steady chain reaction
57
What are the features of a nuclear reactor
- moderator - fuel rods - control rods - coolant
58
Describe the moderator’s role
- slows down neutrons released in fission reactions to thermal speeds through elastic collisions between moderator atom nuclei and fission neutrons
59
How does the moderator slow down neutrons to thermal speeds
Through elastic collisions between moderator atom nuclei and fission neutrons
60
Why should moderator atoms and neutrons be close in size
The larger proportion of momentum transferred, so lower number of collisions to get neutrons to thermal speeds
61
What size should moderator atoms and neutrons be comparatively
Similar size
62
What substances are used as a moderator
Water or graphite
63
Why is water used as a moderator
It’s similar to neutron size, cheap and unreactive
64
What’s the role of control rods
Absorbs neutrons in reactor to control chain reaction
65
What substances are used as control rods and why
Boron or cadmium as they don’t undergo fission
66
What about control rods is controlled
The height
67
What the role of the coolant
Absorbs heat released during fission reactions in core
68
What is the heat from reactor core used for
Make steam which powers electricity generating turbines
69
What is used as a coolant
Water
70
Why is water used as a coolant
Has a high specific heat capacity so transfers lots if thermal energy
71
What does halving a high specific heat capacity mean
Transfer lots if thermal energy
72
What can be used as a coolant (not water)
Molten salt or gas
73
Define nuclear fusion
2 smaller nuclei join together to from 1 larger nucleus
74
Why is energy released in fusion
Larger nucleus has a higher binding energy per nucleon
75
Why are high temperatures needed for fusion
To overcome the electrostatic force of repulsion between nuclei
76
Define binding energy
The work done to split a nucleus into its constituent nucleons

AQA A Level Physics Paper 2 Topics (1 decks)

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