Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A Level Physics > Module 6: Chapter 26 - Nuclear Physics > Flashcards

Module 6: Chapter 26 - Nuclear Physics Flashcards

You may prefer our related Brainscape-certified flashcards:
Physics 101 flashcards AP® Physics flashcards
1
Q

What is Einstein’s mass-energy equation?

A

ΔE = Δmc²

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a rest mass?

A

The mass of an object, such as a particle, when it is stationary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the 2 interpretations of Einsteins mass-energy equation?

A
  • Mass is a form of energy
  • Energy has mass
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Explain the interpretation of Einsteins mass-energy equation that states that mass is a form of energy:

A

The interpretation that mass is a form of energy is illustrated well by annihilation, such as that between an electron and a positron. When an electron and a positron meet, they completely destroy each other (annihilation) and the entire mass of the particles is transformed into two gamma photons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Explain the interpretation of Einsteins mass-energy equation that states that energy has mass:

A

The change in mass Δm of an object (or system) is related to the change in its energy ΔE by the equation ΔE = Δmc². A moving ball has kinetic energy, implying that its mass is greater than its rest mass. The same happens to electrons in particle accelerators, since they are travelling close to the speed of light, their mass could be a hundred times greater than their rest mass. Similarly, a decrease in the energy of the system means the mass of the system must also decrease.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

A person with a rest mass 70kg is in a car which accelerates to a steady speed of 15ms⁻¹. Calculate the change in mass

A

8.75x10⁻¹⁴kg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Explain what happens to the mass in the system during radioactive decay:

A

Since energy is released in radioactive decay, there must be an accompanying decrease in mass. The total mass of the daughter nucleus and another particles emitted is less than the mass of the parent nucleus. This decrease in mass Δm is equivalent to the energy released ΔE.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Calculate the total kinetic energy released by the decay of a single carbon-14 nucleus

Mass of Carbon-14 atom: 2.3253914x10⁻²⁶kg
Mass of Nitrogen-14 atom:2.3252723x10⁻²⁶kg
Mass of electron: 0.0000911x10⁻²⁶kg
Mass of electron antineutrino: negligble

A

2.52x10⁻¹⁴ J

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Calculate the minimum energy of a photon released in the annihilation of an electron and a positron

A

8.20x10⁻¹⁴ J

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is pair production?

A

Pair production is the replacement of a single photon with a particle and a corresponding antiparticle of the same total energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Explain how the total rest mass of particles before the reaction compares to the total rest mass of particles after the reaction:

A

The total rest mass of particles after the collision is greater than that before. The increase in Δm multiplied by c² must be equal to the minimum kinetic energy of the colliding protons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Compare the increase in the mass of an electron accelerated through a potential difference of 1.0MV with its rest mass

A

1.78x10⁻³⁰ kg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why can’t nuclear reactions be simply described in terms of conservation of energy?

A

In alpha decay, the parent nucleus emits an alpha particle, creating a daughter nucleus which recoils int he spposite direction to the alpha particle. As the alpha particle and daughter nucleus have kinetic energy, you cannoy simply use the conservation of energy to describe this. Therefore it makes more sense to describe it in terms of conservation of mass-energy.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the conservation of mass-energy?

A

In any closed system, the total amount of mass and energy is conserved. Any change in energy is accompanied by a change in the mass (and vice versa)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How does the Large Hadron Collider at CERN work?

A

It uses particle accelerators to cause hadrons travelling at incredibly high speeds to collide with each other. Their kinetic energy is transformed into matter.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is one atomic mass unit?

A

One atomic mass unit is one-twelth the mass of a neutral atom of Carbon-12

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the numerical value of one atomic mass unit?

A

1.661x10⁻²⁷ kg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the mass defect?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is binding energy?

A

Binding energy is the minimum energy required to completely separate a nucleus into its constituent protons and neutrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is a more useful quantity than binding energy?

A

Binding energy per nucleon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is Binding energy per nucleon

A

The binding energy of a nucleus per number of nucleons in the atom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How can you calculate the binding energy of a nucleus?

A

It is the energy equivalent of the mass defect
binding energy of nucleus = mass defect x c²

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

The mass of a uranium-235 atom (atomic number of 92) is 235.004393u. Calculate the binding energy in MeV

A

1780MeV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the rest mass of a proton?

A

1.673x10⁻²⁷kg

25
Q

What is the rest mass of a neutron?

A

1.675x10⁻²⁷kg

26
Q

How does the binding energy per nucleon relate to the stability of the nucleus?

A

The greater the binding energy per nucleon, the more tightly bound are the nucleons within the nucleus, and therefore the more stable the nucleus

Greater binding energy per nucleon = greater stability

27
Q

Explain why the total mass of the separated nucleons must be greater than the mass of the nucleus

A

All nucleons are bound together by the strong nuclear force, therefore they can only be separated by doing work to overcome that force. According to Einsteins mass-energy equation, energy and mass are equivalent, therefore the total mass of the separated nucleons must be more than the mass of the nucleus

28
Q

How do you represent a unified atomic mass unit?

A

u

29
Q

If you could construct a nucleus from its nucleons what would happen?

A

Energy would be released, most likely in the form of a photon

30
Q

What is the most stable isotope in nature?

A

Iron-56

31
Q

What is induced nuclear fission?

A

A process in which a large nucleus becomes unstable and splits into two smaller nuclei after absorbing a neutron

32
Q

What is nuclear fusion?

A

A process in which two smaller nuclei join together to form one larger nucleus

33
Q

What happens to the binding energy per nucleon as nucleon number (A) increases?

A
  • For nuclei with A < 56, the BE per nucleon increases as A increases
  • For nuclei with A > 56, the BE per nucleon decreases as A increases
34
Q

Why is Iron-56 the most stable isotope in nature?

A

It has the greatest Binding energy per nucleon of any nucleus

35
Q

Explain how energy is released in natural radioactive decay:

A

In cases of spontaneous decay, the total binding energy of the parent nucleus is less than the binding energy of the daughter nucleus and the alpha particle. The difference is the energy released in decay as kinetic energy

36
Q

Explain how energy is released in nuclear fusion:

A

In a fusion process, two low nucleon number nuclei join together to form a higher nucleon number nucleus. The newly formed nucleus has much greater binding energy than the initial nuclei and therefore energy is released.

37
Q

Explain how energy is released in nuclear fission:

A

In a fission process, a high nucleon number nucleus splits into two lower nucleon number nuclei. The total mass of the particles after the fission reaction is always less than the total mass of the particles before the reaction. The difference in mass Δm corresponds to the energy ΔE released in the reaction. To put this another way, the total binding energy of the particles after fission is greater than the total binding energy before it. The difference in the binding enegies is equal to the energy released.

38
Q

What is a thermal neutron?

A

A neutron in a fission reactor with mean kinetic energy similar to the thermal energy of particles in the reactor core - also known as a slow neutron

39
Q

What is a slow neutron?

A

A thermal neutron

40
Q

What is the most common fuel used in nuclear power stations?

A

Uranium

41
Q

Compare how different Uranium isotopes are suitable for induced nuclear fission:

A
  • Uranium-238 is more likely to capture the neutrons than to undergo fission
  • Uranium-235 easily undergoes fission on absorbing a slow neutron
42
Q

Compare how different Uranium isotopes can undergo spontaneous fission:

A
  • Uranium-238 and Uranium-235 can both split spontaneously without absorbing neutrons, but this is very rare
  • Uranium-236 nuclei have a much greater chance of splitting spontaneously
43
Q

What is the typical induced fission reaction of uranium-235 by a thermal neutron?

A

First 2 steps are always the same, but it can split into a range of daughter nuclei

44
Q

The total mass of the particles after the fission reaction is always less than the total mass of the particles before the reaction. What does this mean in terms of binding energy?

A

The total mass of the particles after the fission reaction is always less than the total mass of the particles before the reaction. The difference in mass Δm corresponds to the energy ΔE released in the reaction. To put this another way, the total binding energy of the particles after fission is greater than the total binding energy before it. The difference in the binding enegies is equal to the energy released.

45
Q

In what form is energy released in a fission reaction?

A

Kinetic energy

46
Q

What is a chain reaction?

A

A chain reaction is a reaction in which the neutrons from an earlier fission stage are responsible for further fission reactions leading to an exponential growth in the rate of the reaction

47
Q

What are the key components of a fission reactor?

A
  • Control rods
  • Fuel rods
  • Moderator and coolant
  • Heat exchanger
  • Concrete shield
  • Turbines
  • Reactor core
48
Q

What is the role of fuel rod’s in a fission reactor?

A

Fuel rods contain the fissile material. They are usually composed of enriched uranium which consists of mainly uranium-238 with 2-3% uranium-235

49
Q

What is the role of the moderator in a fission reactor?

A

The role of the moderator is to slow down the fast neutrons produced in fission reactions. The material for a moderator must be cheap and readily available, and must not absorb any of the neutrons in the reactor. Induced fission of uranium-235 produces fast neutrons and the chance of them being absorbed is quite small, whereas thermal neutrons have a greater chance of producing induced fission. Fast-moving electrons just bounce off the massive uranium nuclei with a negligible loss in kinetic energy. However, when they collide with protons (or deuterium) in water or with carbon nuclei, they transfer significant kinetic energy and slow down. Water and carbon are therefore good candidates for a moderator.

50
Q

What does the binding energy per nucleon against nucleon number curve look like?

A
51
Q

What is the role of control rods in a fission reactor?

A

The control rods are made of a material whose nuclei readily absorb neutrons, most commonly boron or cadmium. The position of the control rods is automatically adjusted to ensure that exactly one slow neutron survives per fission reaction. This is known as a controlled chain reaction. To slow down or completely stop the fission, the rods are pushed further into the reactor core. This is important as otherwise the rate of energy release would grow exponentially with time which could lead to catastophic effects.

52
Q

How is plutonium-239 produced in nuclear fission reactors?

A

Neutrons of intermediate kinetic energies are readily absorbed by uranium-238 nuclei within the fuel rods. These nuclei of uranium-239 quickly decay into nuclei of plutonium-239

53
Q

What is the environmental impact of nuclear fission reactors?

A

Plutonium-239 is produced within fission reactors and is one of the most hazardous materials produced. It is highly toxic and radioactive, having a half life of 24 thousand years, the daughter nuclei produced from its numerous fission reactions are also radioactive. Radioactive waste is therefore highly radioactive and must be buried deep underground for many centuries because isotopes with long half-lives must not enter our food and water supplies. The burial locations must also be geologically stable, secure from attack, and designed for safety. This is important for both out own and future generations.

54
Q

What are the conditions requried to make nuclei fuse together?

A
  • They must be brought close together, 10⁻¹⁵m, so that the short-ranged strong nuclear force can attract them into a larger nucleus
  • All nuclei have a positive charge, so they will repel each other. The repulsive electrostatic force between nuclei is enourmous at small separations.
  • At low temperatures, the nuclei cannot get close enough to trigger fusion. At higher temperatures, they move faster and can get close enough to absorb each other through the strong nuclear force
55
Q

Write the nuclear equations for each fusion reaction that takes place

A
56
Q

What is the proton-proton cycle / hydrogen-burning cycle?

A

It is a nuclear fusion cycle/sequence that is one of the main production routes for helium in stars

57
Q

Why are there no power stations using fusion on earth yet?

A

The main problems are caused by:
* Maintaining high temperatures for long enough to sustain fusion
* Confining the extremely hot fuel within a reactor.

Currently, experimental fusion reactors produce energy for a very short period of time and in much smaller quantities than must be supplied to start the reaction.

58
Q

Why can’t fusion occur at low temperatures?

A

At low temperatures, the nuclei will be travelling too slowly to be able to get clsoe enough for the strong nuclear force to bring about fusion.

59
Q

Calculate the energy released in the fusion reaction of two deuterium nuclei to form a helium nucleus

A

3.8x10⁻¹² J

A Level Physics (29 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions