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Physics GCSE > Nuclear Physics > Flashcards

Nuclear Physics Flashcards

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1
Q

Describe the basic structure of an atom

A

nucleus containing protons and neutrons, around which electrons orbit in fixed energy levels/shells

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2
Q

Describe the plum pudding model of the atom

A

Sphere of positive charge with negative electrons embedded in it

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3
Q

What charges do protons, neutrons and electrons carry?

A

Protons = positive
Neutrons = no charge
Electrons = negative

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4
Q

Why do atoms have no overall charge?

A

Equal numbers of positive protons and negative electrons

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5
Q

What is the radius of an atom?

A

around 1x10^-10m

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6
Q

What is ionisation?

A

Process which adds or removes electrons from an atom

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7
Q

What is the mass number of an element?

A

Number of protons + number of neutrons

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8
Q

Which particle do atoms of the same element always have the same number of?

A

protons

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9
Q

What are isotopes?

A

Atoms of the same element (same number of protons) with different numbers of neutrons

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10
Q

What were the two main conclusions from the alpha particle scattering experiment?

A
  • most of the mass of an atom is concentrated in the nucleus
  • nucleus is positively charged
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11
Q

What are the three types of nuclear radiation?

A

alpha, beta and gamma

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12
Q

Which type of nuclear radiation is the most ionising?

A

alpha

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13
Q

What is the range in air of alpha, beta and gamma radiation?

A

a few cm, 1m and unlimited, respectively

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14
Q

what are the equation symbols for alpha and beta particles?

A

4 0
a and β
2 -1

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15
Q

What is meant by the half-life of a radioactive source?

A

time taken for half the unstable nuclei to decay or the time taken for the count rate to halve

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16
Q

What is radioactive contamination?

A

unwanted presence of substances containing radioactive atoms on or in other materials

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17
Q

Where does background radiation come from?

A

rocks
cosmic rays
fallout from nuclear weapons testing
nuclear accidents

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18
Q

Why are gamma-emitting sources used for medical tracers and imaging?

A

gamma rays pass through the body without causing much damage to cells

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19
Q

What is nuclear fusion?

A

when two light nuclei join to make a heavier one

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20
Q

How does nuclear fission occur?

A

an unstable nucleus absorbs a neutron, it splits into two smaller nuclei, and emits two or three neutrons plus gamma rays

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21
Q

Why is Rutherford’s alpha scattering experiment so important?

A

It led to the discovery of the nucleus and changed the model of the atom

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22
Q

Complete the sentence on the alpha scattering experiment: Most of the alpha particles passed straight through …

A

therefore the atom is mostly empty space

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23
Q

Complete the sentence on the alpha scattering experiment: Some of the alpha particles are deflected …

A

therefore the central nucleus is where charge is concentrated

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24
Q

Complete the sentence on the alpha scattering experiment: A very small number are backscattered/have a large angle scattering …

A

Nucleus is very small + massive (lots of mass) as well as being where charge is concentrated

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25
Q

Definition of an energy level

A
  • exists at a particular distance from the nucleus and contains electrons with a certain defined energy (all the same)
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26
Q

What happens to the energy levels the further they are from the nucleus?

A

They have higher energy

27
Q

Can electrons move between energy levels?

A

Yes, by gaining/losing exactly the right amount of energy

28
Q

What is nuclear radiation?

A

Particles of energy (photons) emitted (given out) by an unstable nucleus

29
Q

What does an alpha particle consist of?

A

2 protons and 2 neutrons

30
Q

What is the charge of an alpha particle?

A

+2

31
Q

What is the range in air of an alpha particle?

A

a few cm

32
Q

Penetration of alpha particles

A

stopped by a sheet of paper (layer of dead skin cells on outside)

33
Q

Ionising power of alpha particles

A

very high

34
Q

What do beta particles consist of?

A

fast electron (close to speed of light)

35
Q

Charge of beta particle

A

-1

36
Q

Range in air of beta particle

A

10s of cm

37
Q

beta particle penetration of materials

A

stopped by couple of mm of Al

38
Q

Ionising power of beta particle

A

quite ionising

39
Q

What does a gamma ray consist of?

A

high frequency energy photon

40
Q

charge of gamma ray

A

0

41
Q

Range in air of gamma ray

A

near infinite

42
Q

Gamma ray penetration of materials

A

reduced by v thick lead or several feet of concrete

43
Q

ionising power of gamma ray

A

low

44
Q

Neutron consists of

A

a neutron

45
Q

charge of a neutron

A

0

46
Q

Which types of radiation are uncharged?

A

neutron and gamma

47
Q

which type of radiation consists of positively charged particles?

A

alpha

48
Q

Which type of radiation consists of negatively charged particles?

A

beta

49
Q

Which type of nuclear radiation does not ionise substances?

A

neutron

50
Q

Which type of nuclear radiation has the greatest ionising effect?

A

Alpha

51
Q

Which type of nuclear radiation travels the furthest in air?

A

neutron

52
Q

Definition of activity

A

The total number of radioactive events (alpha, beta, gamma or neutron radiation) taking place per second

53
Q

Definition of count rate

A

Number of radioactive events picked up by the detector per second

54
Q

Which is bigger, activity or count rate, and why?

A

Activity is bigger
- not all radiation enters the detector
- some radiation passes through without ionising - not picked up

55
Q

Units for activity and count-rate (they are the same)

A

Becquerel (Bq)

56
Q

How is count rate detected?

A

With a Geiger counter

57
Q

Definition of half-life

A

The time taken for the activity of a sample to drop to half of the original value

58
Q

Place the types of radiation in order of most to least damaging if someone is irradiated by it

A

Most:
gamma
beta
alpha (stopped by skin)

59
Q

Place the types of radiation in order of most to least damaging if someone is contaminated by it

A

Most:
alpha (all of the radiation/energy absorbed by the body)
beta
gamma

60
Q

Definition of fission

A

the process during which a large unstable nucleus splits to form 2 smaller fragment nuclei and neutrons

61
Q

What is a chain reaction in fission?

A

A single reaction causes further reactions in this case by releasing neutrons which trigger further fission events. Usually chain reactions result in a very rapid increase in the rate of release of energy - this needs to be controlled to be safe

62
Q

Definition of fusion

A

The process by which 2 light nuclei join together producing a more massive nucleus and lots of energy

63
Q

Advantages of fusion reactors

A
  • The fuel (hydrogen) is present in sea water
  • the product in an inert, harmless gas - Helium
  • BUT it is very difficult
64
Q

Nuclear fusion in the sun

A

Hydrogen fuses to form helium

Physics GCSE (10 decks)

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