Brainscape's Knowledge GenomeTM

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


See full index

Physics > Topic 3: Radioactivity and Astronomy > Flashcards

Topic 3: Radioactivity and Astronomy Flashcards

1
Q

Give an approximation for the radius of

an atom.

A

1x10-10 metres

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

What are the three subatomic

constituents of an atom?

A
  1. Proton
  2. Neutron
  3. Electron
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Where is most of the mass of an atom

concentrated?

A

In the nucleus.

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

Approximately what proportion of the

total radius of an atom is the radius of the nucleus?

A

1/10,000

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

Describe the arrangement of protons,

neutrons and electrons in an atom.

A

● Protons and neutrons are found in the
atom’s nucleus
● Electrons are found in discrete energy
levels around the nucleus

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

What type of charge does the nucleus of an atom have? Why?

A

● Positive charge
● The nucleus contains protons and neutrons
● Protons have a positive charge
● Neutrons have no charge

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

Give two ways that an atom’s electron

arrangement can be changed.

A
  1. Absorbing electromagnetic radiation

2. Emitting electromagnetic radiation

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

Explain how an atom’s electron
arrangement changes when it absorbs
EM radiation.

A

● Electrons move to higher energy levels

● They move away from the nucleus

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

Explain how an atom’s electron
arrangement changes when it emits EM
radiation.

A

● Electrons move to a lower energy level

● They move towards the nucleus

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

How does the ratio of electrons to
protons in an atom result in the atom
having no overall charge?

A

● The number of protons is equal to the
number of electrons
● Protons and electrons have equal and
opposite charges, so charge cancels

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

What do all forms of the same element

have in common?

A

The number of protons.

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

What is the name given to the number of

protons in an atom?

A

Atomic Number

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

What is an atom’s mass number?

A

The total number of protons and

neutrons in the atom.

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

What is an isotope of an atom?

A

An atom of an element that has a
different number of neutrons, but the
same number of protons.

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

What property differs between isotopes

of an atom?

A

The mass of the atom.

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

How do atoms turn into positive ions?

A 
● They lose one or more of their outer
electrons
● Electrons are negatively charged, so
the resultant charge of the atom is
positive
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the relative masses of a

proton, neutron and electron?

A

● 1 - proton
● 1 - neutron
● 1/1850 - electron

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

What is the relative charge of a proton?

A

+ 1

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

What is the relative charge of an electron?

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

State four types of nuclear radiation.

A
  1. Alpha particles
  2. Beta particles
  3. Gamma rays
  4. Neutrons
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is meant by background radiation?

A

● Radiation that is always present

● It is in very small amounts and so not harmful

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

Give 4 sources of background radiation.

A
  1. Rocks
  2. Cosmic rays from space
  3. Nuclear weapon testing
  4. Nuclear accidents
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How do you measure and detect

background radiation?

A
  1. Photographic film

2. Geiger-Muller counter

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

How is photographic film used to

measure radiation?

A

A photographic film turns dark when it absorbs
radiation. This is useful for people who work on
radiation as the more radiation they are exposed
to, the darker the film becomes. Therefore the
workers know when they have been exposed to too much radiation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

How is Geiger-Muller tubes used to measure radiation?

A

When the Geiger-Muller tube absorbs radiation it
produces a pulse, which a machine uses to count
the amount of radiation. The frequency of the
pulse depends on how much radiation is present.

A high frequency would mean the tube is
absorbing a large amount of radiation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What constitutes an alpha particle?

A

● Two protons and two neutrons

● It is the same as a helium nucleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is the range of an alpha particle

through air?

A

A few centimetres (normally in the range of 2-10cm).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What will block beta radiation?

A

● A thin sheet of aluminium

● Several metres of air

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What will block gamma radiation?

A

● Several centimetres of lead

● A few metres of concrete

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Which type of radiation is most ionising?

A

Alpha radiation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Which type of radiation is least ionising?

A

Gamma radiation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

How does gamma emission affect

mass/charge of an atom?

A

Both mass and charge remain unchanged.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Describe the plum-pudding model of the atom

A

A sphere of positive charge, with the

negatively charged electrons distributed evenly throughout it.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Prior to the discovery of the electron

what was believed about the atom?

A

The atom was believed to be indivisible.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Which experiment led to the plum-pudding model being discarded?

A

Rutherford’s alpha-Scattering experiment.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What is the name given to the currently accepted model of the atom?

A

The Bohr model.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Describe Rutherford’s experiment

A

● Alpha particles (charge +2) were fired at a thin
sheet of gold foil
● Most particles went straight through
● Some particles were deflected by small angles
(< 90o)
● A few particles were deflected by large angles
(> 90o)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What are the conclusions of Rutherford’s experiment?

A

● Most of an atom is empty space
● The nucleus has a positive charge
● Most of the mass is concentrated in
the nucleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What happens in the process of beta plus decay?

A

A proton turns into a neutron and a

positron (in order to conserve charge).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What is the process called when a neutron changes into a proton and an electron?

A

Beta minus decay.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

When alpha decay occurs, what happens to the atomic number and the mass number of the atom?

A

● The atomic number decreases by 2
● The mass number decreases by 4
● A new element is made since the
atomic number has changed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What effect does beta minus decay have
on the mass number and atomic number
of an atom?

A

● The mass number stays the same as the total
number of neutrons and protons hasn’t changed (one has just turned in the other).
● The atomic number increases since there is one more proton.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Define the activity of an unstable

nucleus.

A

Activity is the rate at which a source of unstable nuclei decays.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

What is the unit of radioactive activity?

A

Becquerel (Bq)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

What is count-rate?

A

The number of radioactive decays per

second for a radioactive source.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

Give an example of a detector that may be used to measure count-rate.

A

Geiger-Muller tube

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

Describe the nature of radioactive decay.

A 
● Random
● Which nuclei decays and when is
determined only by chance
● It is impossible to predict which nuclei
will decay and when
48
Q

Define the half-life of a radioactive

isotope.

A 
● The time it takes for the number of
unstable nuclei in a substance to halve
● The time it takes for the count rate
from a sample to fall to half its initial
level
49
Q

Give example uses of radioactivity.

A

● Household fire alarms (smoke)

● Irradiating food

● Sterilisation of equipment

● Tracing and gauging thicknesses of materials

● Diagnosis and treatment of cancer

50
Q

How do smoke alarms work?

A

● A radioactive substance is in the alarm which emits
alpha radiation

● The emitted alpha particle ionises the air in the detector and causes a current to flow between the plates

● When smoke interferes with the radiation, the air is no longer ionised and so no current can flow

● This reduction in current flow triggers the alarm

51
Q

State two uses of nuclear radiation in the

field of medicine.

A
  1. Examining of internal organs

2. Radiotherapy in the treatment of cancer

52
Q

What is the role of beta radiation in

tracers?

A

● The tracer is inserted in your body, and targets a specific part of the body

● The radioactive substance in the tracer
releases beta radiation which can be detected by external machines

53
Q

How is beta radiation used to determine thickness?

A

● A beta source is placed above the material and a
detector is placed below it
● If there is an increase in radiation detected by the
detector, too much radiation is passing through the
material, and so it is too thin
● If there is a decrease in radiation is detected, then the material blocks too much radiation, and so it is too
thick

54
Q

Why is ionising radiation dangerous?

A

● It can damage tissue and kill cells

● It can cause cell mutations

55
Q

What is a consequence of cell mutation?

A

Cancer.

56
Q

What precautions should people take

when using ionising radiation?

A

● Avoid handling the source directly (use tongs)

● Wear radiation protective clothing

● Keep the radiation in lead containers to reduce
the amount of radiation that can escape

● Keep exposure time to a minimum

57
Q

Does a long half life or a short half life

make a source more dangerous?

A

If it has a long half life then it would
remain highly radioactive for longer
therefore making it more dangerous.

58
Q

What precautions are taken to reduce

harm for doctors and patients using ionising radiation?

A

● Only a small dose is given to the patient so they are not exposed to too much.

● The radiation used has a short half life so it won’t remain highly radioactive for long. This reduces the risk to the doctors using it as well as the patient.

● Doctors and patients (when applicable) wear protective clothing

59
Q

What is radioactive contamination?

A

The presence of unwanted radioactive

nuclei on other materials.

60
Q

What is irradiation?

A

● The process of exposing a material to
nuclear radiation

● The material does not become
radioactive

61
Q

How is a radioactive tracer used in

medicine?

A

● The tracer is placed inside the body (it can be in a drink, eaten or injected)
● The tracer releases gamma radiation which is
detected by a detector which moves around the body
● This can then be used to produce a picture of the
patient’s body

62
Q

How does a PET scanner work?

A

● PET (positron emission tomography) uses a
tracer, which is injected into the patient’s body
● The scanner detects the gamma rays which
are released by the trace
● Multiple images are taken and this is used to
form a 3D image of the patient’s body

63
Q

Isotopes are used in PET scanners.

What is important about where they are produced and why?

A

They must be produced near the hospital
because the isotopes used have a short
half life so must be used soon after production.

64
Q

Describe the advantages of nuclear

power for generating electricity.

A

● Nuclear fuels do not produce carbon dioxide
● The fuel is readily available, so would reduce strain on the fossil fuel supplies
● Less nuclear fuel has to be used to produce the same amount of energy as burning fossil fuel
● Does not contribute to global warming

65
Q

Explain some disadvantages of using

nuclear power to generate electricity.

A

● Unpopular - the public perceive nuclear power as very dangerous
● Security risks as the radioactive substances can be useful for terrorists
● Expensive to commission and decommission the stations - which may be bad for a country’s economy
● The radioactive waste can be difficult to dispose of and will remain radioactive for many years - which can be dangerous to humans and the environment
● Risk of nuclear accidents

66
Q

What is nuclear fission?

A

The splitting of large, unstable nuclei to

form smaller more stable nuclei (+ the emission of spare neutrons).

67
Q

What usually needs to happen to induce

fission?

A

● The unstable nuclei must absorb a
neutron
● Spontaneous fission (where no
neutron absorption occurs) is rare

68
Q

Alongside two smaller nuclei, what else is emitted in a fission reaction?

A

● Two or three neutrons
● Gamma rays
● Energy

69
Q

Name a common fissile nuclei.

A

Uranium-235

70
Q

What are the three main components of the core a nuclear reactor?

A
  1. Fuel rods
  2. Control rods
  3. Moderator
71
Q

What takes place during a chain reaction in a nuclear reactor?

A 
● An unstable nucleus absorbs a neutron
● The nucleus undergoes fission and
releases 2 or 3 further neutrons
● These induce more fission, which results
in a chain reaction
72
Q

What is the consequence of an

uncontrolled chain reaction?

A

● The rate of fission events becomes to
high and results in the production of too much energy
● This can lead to a nuclear explosion

73
Q

How is the chain reaction in a fission reactor kept under control?

A

● Control rods are positioned in between the fuel
rods
● The rate of fission is controlled by moving
these rods up and down
● The lower the rods are inserted, the slower the
rate of fission

74
Q

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

A

To slow down the neutrons so they are
travelling at speeds which allow them to
be absorbed by fissile nuclei and cause fission.

75
Q

How is electricity produced in a nuclear

power station?

A

● The reactions release thermal energy
● The thermal energy is used to boil water and
then produce steam.
● This steam is then used to turn a turbine which
starts the generator.

76
Q

What is nuclear fusion?

A

When two light nuclei join to produce a

heavier nucleus and release energy.

77
Q

Name two isotopes of hydrogen which

are commonly used in nuclear fusion.

A

Deuterium and Tritium

78
Q

Which releases more energy, nuclear fission or nuclear fusion?

A

Nuclear fusion.

79
Q

Explain the difficulty of generating

energy through nuclear fusion.

A

Fusion requires very high temperatures
which in itself requires large quantities of
energy. Currently, the production of
fusion results in a net loss of energy.

80
Q

Give an example of where fusion occurs?

A

In the sun - stars use fusion as their energy source.

81
Q

Why does nuclear fusion require so much energy?

A

This is because both nuclei are positive
therefore a lot of energy is required to
overcome the electrostatic repulsion between the two nuclei.

82
Q

Why does your weight vary across planets?

A

● Your weight is dependant on g, since weight = mass x g
● The gravitational field strength (g) of a planet
varies depending on the size of the planet
● This means that your weight will also vary

83
Q

What is gravitational field strength on

Earth?

A

Approximately 10 N/kg.

84
Q

What does our solar system consist of?

A

● The sun (our star)

● 8 Planets (Mercury, Venus, Earth, Mars,
Jupiter, Saturn, Uranus, and Neptune)

● The planet’s natural satellites (ie. the moon)

● Dwarf planets

● Comets and asteroids

85
Q

Name the planets in order, starting with the closest to the sun.

A

Mercury, Venus, Earth, Mars, Jupiter, Saturn,

Uranus, and Neptune

86
Q

What did Ptolemy suggest about the universe?

A

That the earth was at the centre.

87
Q

What did Copernicus suggest about the

universe?

A

That the sun is at the centre and the planets orbit it.

88
Q

What did Galileo contribute to theories about the universe?

A

He used telescopes to support Copernicus’ suggestions about the sun, and suggested that moons orbit planets.

89
Q

Describe the orbits of moons, planets, comets and artificial satellites.

A

They orbit in an elliptical shape.

90
Q

Explain why for a stable orbit, the radius
of orbit must change if the speed
changes.

A

● At higher speeds, the object requires a greater
centripetal force
● For a greater centripetal force, the
gravitational force must increase
● This is achieved by the radius of the orbit
being reduced

91
Q

Explain how the force of gravity acting on

a satellite affects its speed and velocity.

A

● The force can alter its velocity since the
direction is continually changing
● It can’t cause a change of speed since
there is no force component in the direction
of motion

92
Q

Describe the Steady State theory

A

The Steady State theory says that the
universe has always existed but is
expanding and creating matter to
counteract the loss in density.

93
Q

Describe the Big Bang theory

A

The Big Bang theory states that the
universe expanded from a very small
dense point about 14 billion years ago.

94
Q

What is red-shift?

A

A perceived increase in the wavelength

of light due to the source moving away from the observer.

95
Q

What does red-shift provide evidence for?

A

● The universe is expanding

● This supports the Big Bang theory

96
Q

What does the Big Bang theory suggest?

A

The entire universe started from a very

small, hot and dense region in space.

97
Q

Compare the observed red-shift of two

galaxies, one further away than the other.

A

● The galaxy that is further away is
travelling faster
● The observed red-shift is greater the
further away it is

98
Q

What did scientists observe to provide
evidence that the universe is expanding
at an ever faster rate?

A

They observed supernovae, which suggested that galaxies are moving away at an ever faster rate.

99
Q

Prior to observations of supernovae,
what was believed about the rate of
expansion of the universe and why?

A

● The rate of expansion was expected to
occur more slowly
● It was thought that gravitational forces
would cause this slowing down

100
Q

What does CMBR stand for?

A

Cosmic Microwave Background Radiation

101
Q

What does CMBR provide further

evidence for?

A

● The Big Bang Theory
● It is believed that CMBR originates
from radiation produced in the big
bang

102
Q

How does the existence of CMBR

support the expansion of the universe?

A 
● It is thought that gamma radiation was
released in the Big Bang
● The expansion of the universe has
stretched this radiation, resulting in the
microwave radiation present today
103
Q

What factor determines the type of lifecycle a star undergoes?

A

The size of the star.

104
Q

Which two phases do all stars of the

same or greater size than the sun undergo?

A
  1. Protostar phase

2. Main sequence phase

105
Q

What do stars like the sun become at the

end of their life-cycle?

A

A black dwarf.

106
Q

What two things can stars much bigger

than the sun become at the end of their lifecycle?

A
  1. Neutron star

2. Black hole

107
Q

What two phases do stars of similar size
to the sun go through between being a
main sequence star and a black dwarf?

A
  1. Red giant

2. White dwarf

108
Q

What two phases do stars of greater size

than the sun go through between being a main sequence star and a neutron star/black hole?

A
  1. Red supergiant

2. Supernova

109
Q

Describe the transition of the star from

the nebula stage to the main sequence.

A

● The nebula increases in size until it is pulled in due to its gravity, causing GPE to turn into KE

● The collisions between particles cause this kinetic
energy to turn into thermal energy

● Eventually the nebula will become dense and hot
enough to begin fusion

110
Q

What occurs in the stage when a star is a main sequence star?

A

● The fusion in the star releases energy

● This energy balances out with the gravitational
potential energy leaving the star

● The star is in equilibrium so will not collapse
due to gravity or expand due to radioactive behavior. It is stable.

111
Q

What happens when a star transitions to

the red giant stage?

A

● Once all of the hydrogen fuel has been used
up, the star begins to fuse helium and other larger nuclei

● This causes the star to expand and become a
red giant

112
Q

How does a red giant become a white dwarf?

A

● Once all reactions have taken place, the star’s
gravity pulls in all of its mass, making a small, dense white dwarf

● This will cool down to form a black dwarf

113
Q

Why are telescopes located outside the earth’s atmosphere?

A

● The earth’s atmosphere absorbs many
electromagnetic waves, making it difficult to detect certain waves.
● Light pollution can make some images less clear
● Telescopes in space can operate both night and day

114
Q

What is the disadvantage of telescopes

located outside the atmosphere?

A

They are difficult to maintain as they have
to be repaired in space (or brought down,
which is unreasonably expensive).

115
Q

What are the disadvantages of optical telescopes?

A

● They can only be used at night when the sky is clear

● They can’t be used when the weather is cloudy etc.

116
Q

Evaluate the use of radio telescopes.

A

● They are not weather dependent for example
radio waves are not blocked by clouds so can be used in the rain
● They are usually large and expensive

Physics (7 decks)

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