Brainscape's Knowledge GenomeTM

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


See full index

Physics > Radioactivity > Flashcards

Radioactivity Flashcards

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

JJ Thompson Plum Pudding model

A

-discovered that electrons could be removed from atoms
-suggested ‘plum pudding’ model
-atoms are spheres of positive charge with tiny electrons stuck in them

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

Ernst Rutherford Nuclear model

A

-fired beam of alpha particles at thin gold foil
-expected most particles to travel straight through some deflected back
-realised most of mass was concentrated in a tiny positively charged nucleus at centre

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

Niels Bohr Bohr Model

A

-suggested that electrons were in fixed orbits at set distances from nucleus
-called energy levels
-electrons can only exist in these shells and no where else

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

What happens when an inner electron moves up to a higher shell?

A

-absorbs EM radiation with the right amount of energy.
-when it moves up, it moves into an empty or partialy full shell

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

What happens when an inner electron moves down to a lower shell?

A

-Once it has gone up a level, the electron will quickly fall back
-Will emit the same amount of energy it absobred
-energy carried away by EM radiation

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

What happens to the energy levels as you move further from the nucleus?

A

-they get closer together
-means an excited electron falling from the third energy level to the second would release less energy than the same from second to first
-means frequency of the generated radiation decreases as you get further

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

What is released when electrons move between energy levels?

A

-Visible light
-changes within nucleus itslef produce high frequency, high energy gamma rays

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

What is an isotope?

A

An isotope of an element are atoms with the same number of protons but a different number of neutrons

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

What do unstable isotopes do?

A

They decay into other elements and give out radiation as they try to become more stable

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

What are Alpha particles?

A

-are a helium nuclei (two neutrons and two protons)
-emitted from the nucleus
-can only travel a few cm in air
-absorbed by a thin sheet of paper
-because of their size, they are strongly ionising

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

What are Beta minus particles?

A

-beta minus particle is just a fast moving electron released by the nucleus
-both moderately ionising
-beta minus have can travel a few metres in air
-absorbed by a sheet of aluminium 5mm thick

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

What are Beta plus particles?

A

-beta plus particle is a fast moving positron (antiparticle of electron). has the same mass just a positive charge
-moderately ionising
-have a smaller range, because when they hit an eletron the two destroy each other and produce gamma rays

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

What is annihilation?

A

-When a beta plus particle hits an electron, they destroy each other
-produces gamma rays
-used in PET scanning

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

What are gamma rays?

A

-waves of EM radiation released by the nucleus after it undergoes nuclear rearrangement
-penetrate far into materials and travel a long distance through air
-they are weakly ionising as they pass through rather than collide with atoms
-can be absorbed by thick sheets of lead or metres of concrete

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

In nuclear equations, Alpha decay….

A

-decreases charge and mass of the nucleus
-mass number decreases by 4
-atomic number decreases by 2

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

In nuclear equations, Beta minus decay….

A

-increases the charge of the nucleus
-mass number doesn’t change
-atomic number increases by 1

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

In nuclear equations, Beta plus (positron) emission….

A

-decreases charge of the nucleus
-mass number doesn’t change
-atomic number decreases by 1

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

In nuclear equations, neutron emission….

A

-decreases the mass of the nucleus
-the mass number stays the same
-the atomic number stays the same

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

In nuclear equations, gamma rays….

A

-Don’t change the charge or mass of the nucleus
-they are a way of getting rid of excess energy from an atom

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

what is background radiation?

A

-The low level radiation thats around us all the time
-The radioactivity of naturally occurring unstable isotopes all around us

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

what is radiation from space?

A

-Cosmic rays
-Mostly come from the sun
-Earth’s atmosphere protects us from much of this radiation

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

what is radiation due to human activity?

A

-fallout of nuclear explosions or radiation from nuclear waste etc.
-This represents a tiny proportion of the total background radiation

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

what do radioactive sources contain?

A

-contains radioactive isotopes that give out radiation from the nuclei of their atoms
-process is entirely random

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

how is activity measured?

A

-measured in becquerels (Bq)
-1 Bq = 1 decay per second

25
Q

How can activity be measured

A

-with a Geiger-Muller tube which clicks each time it detects radiation
-can be attached to a counter, which displays num. of clicks per second (count rate)

26
Q

Difference between irradiation and contamination

A

-EXPOSURE to radiation is called IRRADIATION
-RADIOACTIVE PARTICLES getting onto objects is called CONTAMINATION

27
Q

what is irradiation?

A

-Objects near a radioactive source are irradiated by it.
-Means they are exposed to it (e.g background radiation)
-Irradiating something does not make it radioactive

28
Q

how to prevent irradiation on an object/human?

A

-keeping sources in a lead-lined box
-standing behind barriers
-being in a different room
-medical staff who work with irradiation wear photographic film badges to monitor exposure

29
Q

what is contamination?

A

-when unwanted radioactive atoms get onto an object, the object is contaminated
-these contaminating atoms might decay, releasing radiation which could cause harm

30
Q

why is contamination especially dangerous?

A

-as radioactive particles could get inside your body
-this releases radiation inside your body

31
Q

how to stop or prevent contamination?

A

-once a person is contaminated, contamination must be removed fully or all radioactive atoms must decay before they are safe again
-gloves and tongs should be used when handling sources to avoid particles getting stuck in skin or under your nails

32
Q

what is the most and least dangerous radiation outside the body?

A

-beta and gamma radiation
-as they can penetrate the body and get to the organs
-alpha is less dangerous, because it can’t penetrate the skin

33
Q

what is the most and least dangerous radiation inside the body?

A

-alpha are the most dangerous
-as they are strongly ionising, they do all their damage in a very localised area
-means contamination is the main concern when working with alpha sources

34
Q

How is alpha radiation used?

A

-A weak source of alpha radiation is placed in a smoke detector, close to two electrodes
-The source causes ionisation, and a current of charged particles flows
-If there is a fire then smoke will absorb the charged particles - the current falls and the alarm sounds

35
Q

How are gamma rays used?

A

-Food can be irradiated with a high dose, killing all microbes
-Medical equipment can be sterilised using gamma rays instead of boiling

36
Q

Why is irradiation a good method of sterilisation?

A

-As, unlike boiling, it doesn’t involve high temp.
-Allows fresh fruit or plastic instruments to be sterilised without damage

37
Q

How is radiation used in tracers medically?

A

-Weakly ionising beta or gamma emitters can be used to detect and diagnose medical conditions without causing too much damage to the body
-They should have a short half life so that the radioactivity quickly disappears

38
Q

How are tracers used non-medically?

A

-Gamma emitting tracers can be used in industry to detect leaks in underground pipes
-Beta radiation is used in thickness control of paper rollers.

39
Q

How is PET scanning used?

A

Used to diagnose illnesses and show tissue/organ function:
-identify active tumours by showing metabolic activity

40
Q

How does PET scanning work?

A

1) Inject patient with a positron emitting radioactive isotope

2) positrons annihalate electrons in an organ, emitting high energy gamma rays in opposite directions

3) detectors pick up the gamma rays, allowing them to identify where the tumour is

41
Q

In PET scanning, why does the distribution of radioactivity match metabolic activity?

A

more of the radioactive glucose is taken up by cells that are doing more work (cells with increased metabolism)

42
Q

How are radiotherapy treatments delivered internally?

A

-alpha emitters are put near a tumour as it is highly ionising, damaging cancerous cells
-does limited damage to normal tissue as it has a short range

43
Q

How are radiotherapy treatments delivered externally?

A

-using gamma rays aimed at the tumour
-they are able to penetrate through the patient’s body and damage majority cancerous cells

44
Q

How does nuclear fission chain reaction work?

A

-A slow moving neutron is fired at a large, unstable nucleus (uranium-235)

-The neutron is absorbed by the nucleus, making the atom more unstable, causing it to split

When U-235 atom splits, it forms two new lighter elements (daughter nuclei) and energy is released

-Each time a uranium atom splits up, it also spits out multiple neutrons, which hit other unstable U-235 atoms, repeating the cycle

45
Q

Why can a neutron be absorbed by the nucleus?

A

Because it has a neutral charge, meaning it is not repelled by the positive charge of the nucleus

46
Q

What does a control rod do?

A

-Limits the rate of fission by absorbing excess neutrons
-Creates a steady rate of nuclear fission, where each fission produces another fission

47
Q

What does a moderator do?

A

Slow down fast moving neutrons, allowing a chain reaction to take place

48
Q

What does a fuel rod do?

A

-they contain the unstable radioactive isotope (U-235)
-needed to make thermal neutrons

49
Q

What are thermal neutrons?

A

Slow moving neutrons, capable of maintaining a chain reaction when with an abundance of them

50
Q

How do meltdowns happen?

A

-When a chain reaction in a nuclear reactor is left to continue unchecked
-large amounts of energy is released in a short time, creating many new fissions following each fission
-this causes a runaway reaction which could lead to a meltdown

51
Q

How does nuclear fusion work?

A

-when two light nuclei collide at high speed and fuse to create a larger, heavier nucleus
-hydrogen nuclei can fuse to produce a helium nucleus

52
Q

Why does the nucleus formed in nuclear fusion not have the same mass as the two lighter nuclei?

A

As some of the lighter nuclei is converted into energy and released in the form of gamma rays.

53
Q

Why does fusion only happen at really high pressures and temperatures?

A

-because the positively charged nuclei have to get very close to fuse, as they have to overcome the repelling force of electrostatic attraction

54
Q

Why should we want fusion reactors?

A

As they would only produce helium, meaning that they could solve our energy crisis

55
Q

How does a nuclear power station work?

A

1) energy released by fission is transferred to thermal energy store of moderator

2) this is then transferred to the thermal energy store of the coolant

3) then to the thermal energy store of cold water passing through a boiler

4) causes the water to boil and energy transferred to the kinetic energy store of steam

5) this energy is transferred to the kinetic energy store of a turbine and then to the kinetic energy store of a generator

6)This energy is then transferred away from generator electrically

56
Q

Advantages of nuclear power

A

-fairly safe way of generating electricity
-very reliable energy source
-reduces the need for fossil fuels as nuclear fission does not release greenhouse gases
-huge amounts of energy can be generated from a relatively small amount of nuclear material

57
Q

Disadvantages of nuclear power

A

-Overall cost of nuclear power is high due to initial cost of the power plant and final decommisioning
-Public perception is very negative
-Carries the risk of meltdowns

58
Q
A

Physics (9 decks)

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