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Physics > Nuclear Physics > Flashcards

Nuclear Physics Flashcards

1
Q

Name the three atomic models, and who created them in order

A
  1. Dalton’s model
  2. J.J. Thompson’s model
  3. Rutherfords model
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2
Q

What was Dalton’s model, and how did he come up with it?

A

A circle.
He believed that everything was made of indestructible pieces of matter, because he reasoned if you break a substance down long enough, you will get to a point where matter is too small to break.

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3
Q

What did J.J. Thompson discover, and what model did he make?

A

He discovered that neutral atoms could release negatively charged particles. Therefore, there must be something to counteract the negativity, and therefore be positive. His model was called the Plum Pudding model, as he believed that an atom was composed of a positive sphere, and within are negatively charged particles (electrons).

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4
Q

What experiment did Rutherford make to discover/create the current atomic model)?

A

Rutherford’s Gold Foil Experiment:
He fired a bunch of Alpha particles (Helium Nuclei) at a piece of gold foil (~300 atoms thick), and held a screen to record particles behind it, expecting them to be small enough to go through the gold. The results were:
- Most particles went right through (because there is a lot of empty space)
- Some particles deviated slightly (because they came close to another positive charge)
- ~1/800 shot right back in the opposite direction (because they hit anothe rpositive charge head on)

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5
Q

What were Rutherford’s three conclusions?

A

1) The majority of an atom is empty space
2) There must be a concentrated positive charge in the atom
3) The majority of the mass of an atom most be concentrated in a small space

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6
Q

Def. Radioactive atom

A

Atoms that have unstable nuclei and spontaneously break down.

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7
Q

What are the 3 reasons for instability?

A

1) Too many neutrons
2) Too few neutrons
3) Too much energy

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8
Q

What are the three types of radiation?

A

1) Alpha Radiation
2) Beta Radiation
3) Gamma Radiation

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9
Q

What is Alpha Radiation?

A

When an unstable nuclei spontaneously breaks down and fires the nucleus of a helium atom, a.k.a Alpha Particles. This can be detected when the mass of an atom changes.

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10
Q

What are 3 features of Alpha Particles?

A
  • Travel at about ~10% speed of light
  • Can only travel at about ~10cm before ionising (ripping electrons from other particles) to helium gas
  • Can be blocked by paper
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11
Q

What is the formula to calculate the products from Alpha Radiation?

A

XZA –> YZ - 2A - 4+α24

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12
Q

What is Beta Radiation?

A

When a neutron spontaneously decays into a proton, emitting a beta particle from the nucleus.

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13
Q

What is a Beta particle?

A

An electron

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14
Q

What is the relative atomic mass of a Beta Particle?

A

0

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15
Q

What is the charge of a Beta Particle?

A

-1

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16
Q

What are three characteristics of the Beta Particle?

A
  • Travel at almost the speed of light ~2.9 x 108m/s
  • Can travel through paper
  • Blocked by thin sheet of Aluminium
  • Individually harmless, dangerous in large quantities
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17
Q

What is the formula to calculate the products from Beta radiation?

A

XZA –> YZ + 1A + 0+β-10

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18
Q

What is the formula for neutron decay?

A

n01 –> p+ 11+e-10

Neutron —> Proton + Electron

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19
Q

What is Gamma Radiation?

A

High energy electromagnetice waves with very small wavelengths (Gamma Rays)

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20
Q

What causes Gamma Radiation?

A

When an atom has too much energy, it is released in the form of Gamma Radiation.

Excess energy can be caused by decay

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21
Q

What is the symbol for a Gamma Ray?

A

γ00

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22
Q

What are the characteristics of the Gamma Ray?

A
  • Lowest ionising ability
  • High penetrative ability
  • Blocked by a few cm of lead or a few m of concrete
  • Most dangerous type of radiation due to it’s penetrative ability (it can go through the body, breaking up atoms and causing acute radiation sickness)
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23
Q

What is the formula for Gamma Radiation?

A

XZA –> YZ + 0 A + 0+β00

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24
Q

What are the stages of radiation sickness?

A

1) A few minutes-days after exposition to radioactivity, syptoms of sickness include diarrhea and vomiting.
2) Latent recovery, meaning you feel better
3) You get worse again
4) You die or recover, with higher chance of getting cancer later on

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25
Q

Which type of radiation is the strongest ioniser?

A

Alpha

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26
Q

Which type of radiation has the highest penetrating power?

A

Gamma

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27
Q

Which type of radiation is blocked by 3 mm of Aluminum?

A

Alpha, Beta

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28
Q

Which type of radiation has a neutral charge?

A

Gamma

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29
Q

Which type of radiation has the largest mass?

A

Alpha

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30
Q

Which type of radiation has a negative charge?

A

Beta

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31
Q

Which type of radiation results in an increase of atomic number?

A

Beta

32
Q

Which type of radiation has the slowest speed?

A

Alpha

33
Q

Which type of radiation is blocked by several metres of concrete?

A

Alpha, Beta, Gamma

34
Q

What happens when an alpha particle passes through an electric field perpendicular to the direction of the field?

A

It goes towars the negative side of the field, as it is positives and opposite charges attract

35
Q

What happens when a beta particle passes through an electric field perpendicular to the direction of the field?

A

It goes towars the positive side of the field, as it is negative and opposite charges attract

36
Q

What happens when a gamma ray passes through an electric field perpendicular to the direction of the field?

A

It is unaffected by the field, as it has a neutral charge

37
Q

What happens when an alpha particle passes through a magnetic field perpendicular to the direction of the field?

A

If the magnetic field is coming out of the page, it goes up. Otherwise, it goes down

38
Q

What happens when a beta particle passes through a magnetic field perpendicular to the direction of the field?

A

If the magnetic field is coming out of the page, it goes down. Otherwise, it goes up

39
Q

What happens when a gamma ray passes through a magnetic field perpendicular to the direction of the field?

A

It is unaffected by the magnetic field, as it has no charge

40
Q

Explain the ‘Right Hand Stop Rule’

A

1) Align your fingers with the direction of the magnetic field
2) Hold your thumb at a right angle to your fingers, and align it with the direction of an Alpha or Beta particle
3) If Alpha, the force acting on the particle is the same direction as going out of your palm, and vice versa for Beta

41
Q

What is the minimum lethal dose of radiation?

A

2 Sieverts

42
Q

How many sieverts is one microsievert?

A

1,000,000

43
Q

What are the 4 main sources of background radiation?

A
  • Food
  • Building materials and rocks
  • Radon gas
  • Cosmic rays
44
Q

Explain food radiation

A

Some foods like bananas or walnuts contain radioactive emitters (e.g Potassium-14 (Gamma emitter in bananas) and Radium (in walnuts))

45
Q

Explain building material or rock radiation

A

Building materials/rock can contain radioactiv eemitters such as Radium, Uranium and Thorium.
Anything from the ground can contain traces of these.
E.g. Concrete, Granite or Sand

46
Q

Explain Radon gas radiation

A

Radon gas is one of the stages of Uranium decay with a particularly long half-life. It is mainly produced by Uranium decay in the ground. Large doses can increase the risk of lung cancer. Radon detectors are placed in newly built buildings to make sure the levels of radon are safe.

47
Q

Explain cosmic ray radiation

A

Harmless high energy radiation comes from space, from multiple sources (normally supernovas). If these rays are absorbed by particles in the atmosphere, however, the particles can break down into more harmful ionising particles.

48
Q

Why do you need to adjust the number of sieverts measured when you try to gage how radioactive an object is?

A

There is always a constant background radiation (can vary depending on the place), and if someone tries to measure a specific objects rdiation, they need to adjust the meaured value by taking away the backgound radiation if they want an accurate result.

49
Q

What is the formula to adjust for background radiation?

A

Radiation measurement of object = Total radiation - Background radiation

50
Q

What is the formula to adjust for background radiation?

A

Radiation measurement of object = Total radiation - Background radiation

51
Q

Def. halflife

A

Time taken for half of the nuclei in a sample of radioactive material, to decay

52
Q

Is it possible to predict radioactive decay?

A

It is not possible to predict the decay of individual particles as they decay spontaneously. However, it is possible to predict the probability of when half a sample will decay.

53
Q

After how many halflives do we consider the substance almost completely decayed?

A

5

When drawing a half life graph, add at least 5 halflives.

54
Q

Why do different isotopes have different halflives?

A

Because the more unstable an isotope is, the shorter the halflife, and every isotope has a different stability

55
Q

What is the formula for the number of Nuclei remaining in a decaying substance?

A

Number of nuclei remaining = original amount/2n

n = amount of half lives

56
Q

Why does radioactive decay take a theoretically infinite amount of time to fully decay?

A

Becaus every halflife, the amount of substance left is halved, but if you keep halving infinity, you never get to 0.

In practice, however, eventually there will be not nuclei left

57
Q

What are the 6 uses of radiation?

A
  • Smoke detectors
  • Quality control
  • Fault detection
  • Food irradiation
  • Cancer treatment
  • Organ function & blood flow testing
58
Q

Describe how smoke detectors are one of the uses of radiation

A

Charged alpha particles are emitted from a small sample of Am-241. They land on a detector resulting in a small current flowing.

Smoke interferes with the alpha particles, breaking the flow and setting of the alarm.

59
Q

Am-241 has a half life of 430 years. Why is it used in smoke detectors?

A

So it lasts at least as long as the lifetime of the smoke detector, and does not decay too rapidly.

60
Q

Describe how quality control is one of the uses of radiation

A

A beta emitter can be used to measure (to then adjust) the thickness of materials.

The beta particles are sent throughout the material and if too many pass, this means that then material is too thin. If too few pass, the material is too thick.

Gamma radiation can be used alternatively to measure thicker substances.

61
Q

Describe how fault detection are one of the uses of radiation

A

The substance being tested is covered with X-ray film, then radiatiation is sent to the material. If there are faults, the radiation will pass through them more easily. This radiation is detected by the film, so we can see where the faults are.

62
Q

Describe how food irradiation is one of the uses of radiation

A

Radiating food with UV kills single celled organisms. Therefore, it preserves food e.g. strawberries from mould and parasites.

It is also used in hospitals if patients need completely sterilised food

63
Q

Describe how cancer treatment are one of the uses of radiation

A

Gamma rays and X-rays can be directed to kill tumour cells, a.k.a radiation therapy

This process cannot be done without avoiding a small dose of radiation being sent to other cells

64
Q

Describe how organ function & blood flow testing are one of the uses of radiation

A

Radioactive emitters are injected into the human body (best emitter is gamma because it is the least ionising).

The emitter needs a short half life so it does not remain in the human body for too long.

A detector can then track the movement of the emitter around the body.

65
Q

What are the 3 effects of radiation on living things?

A
  • Cell death
  • Genetic Mutation
  • Cancer
66
Q

Def. Contamination

A

Unwanted presence of materials containing radioactive atoms and other materials

67
Q

Def. Irradiation

A

Process of exposing an object to nuclear radiation. the irradiated object does not bemocme radioactive.

68
Q

How do you store an Alpha emitter safely?

A

Can be stored in a thin package

However, protective clothing should be worn when handling sources of alpha particles as they are very dangerous if they get inside your body.

69
Q

How do you store a Beta emitter safely?

A

Must be stored in a lead/similarly dense metal container

70
Q

How do you store a Gamma emitter safely?

A

Only stopped by thick lead/concrete, so radioactive waste emitting gamma radiation is typically buried deep underground

71
Q

What are the 3 ways to reduce the risk of radiation?

A

Time - Less time spent near the source, less radiation recieved
Distance - Greater distance for the source, less radiation recieved
Shielding - Being behind shielding from the source means less radiation recieved

72
Q

Def. Fission

A

The splitting of large nuclei into smaller nuclei, releasing energy in the process

73
Q

Def. Fusion

A

The joining of small nuclei into larger nuclei, releasing energy in the process

74
Q

What is an example formula for fission?

A

n + U –> Ba + Kr + 3n

75
Q

What is an example formula for fusion?

A

H-2 + H-3 –> He + n

76
Q

During nuclear fusion or fission, what change of mass occurs between products and reactants?

A

In both cases, the products have slightly less mass than the reactants

77
Q

Why can mass be transferred into energy & vice versa?

A

Due to E = mc2

Physics (7 decks)

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