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physics > Radiation - SP6 > Flashcards

Radiation - SP6 Flashcards

1
Q

what is radiation that causes electrons to escape called?

A

ionising radiation

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2
Q

what is the emission spectrum?

A

Each colour is a different wavelength of light that differs for each element on the basis of emision and absorbtion

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3
Q

what are different sources of background radiation

(name most + least common in uk)

A

radon gas (most common)
food + drink
cosmic rays
ground + buildings
medical
nucear (least common)

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4
Q

how is randon gas produced?

A

by small rocks that contain small amounts of uranium

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5
Q

why does background variation differ in different parts of the uk

A

the rock type and building stone vary - hence, so does the mount of radon

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6
Q

what are cosmic rays?

A

High-energy, charged particles stream out of the Sun and other stars

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7
Q

how can radioactivity be detected?

+ how does it work?

A

using photographic film - the film becomes darker and darker as more radiation reaches it

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8
Q

what can be used to measure the radioactivity of a source?

(how does it work?

A

Geiger-Muller (GM) tube - radiation passing through the tube ionises gas inside it and allows a short pulse of current to flow - this can be connected to a counter to count pulses

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9
Q

what is the count rate of the GM tube?

A

number of clicks per second or minute

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10
Q

what are the 4 types of radiation a nucleus can emit when it decays?

A

alpa, beta, positrons, gamma rays

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11
Q
A
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12
Q

what is the compisition of an alpha particle?

+ relative mass and overall charge

A

2 protons and 2 neutrons
relative mass: 4
charge: +2

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13
Q

what is the + relative mass and overall charge of a beta particle

A

relative mass: 0 (or close to anyways)
charge: -1

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14
Q

what is the relative mass and overall charge of a positron?

A

relative mas: 0
charge: +1

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15
Q

what is the relative mass and overall charge of gamma rays?

A

relative mass: 1
charge: 0

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16
Q

the types of radiation (alpha… gamma) are all types of what radiation?

A

ionising and penetrating

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17
Q

At what speeds are alpha particles emitted at? what does this mean in terms of ionising?

mention how mass helps to achieve this

A

emitted at high speeds + high relative mass -> transfer lots of energy + are good at ionising atoms they encounter

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18
Q

what happens every time an alpha particle ionises?

A

it loses energy

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19
Q

why do alpha particles have a short penetration distance?

A

Since they produce many ions in a short distance, they lose energy quick hence, short distance of penetration

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20
Q

how ionising are beta particles in terms of alpha particles?

what does this mean for penetration distance?

A

much less ionising than alpha - penetrate further than alpha can

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21
Q

how ionising are gamma rays in terms of beta rays - what does this mean for penetration distnace?

A

10x less ionising - can penetrate matter easily

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22
Q

how far can each (alpha beta gamma) radiation travel? what is it obstructed by?

A

alpha: few cm - stopped by paper
beta: few meters - stopped by 3mm alminium
gamma: few kilometers - thick lead stops this

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23
Q

what changes when an unstable nucleus changes and emits particles?

what does this mean for the elemnt?

A

atomic number can change and becomes a new element

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24
Q

what happens during beta decay?

A
  • a neutron changes into a proton + an electron
  • electron ejected from atom
  • atom no increases by 1 but there is no change to mass number
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25
Q

what happens in positron decay?

A
  • a proton becomes a neutron and a positron
  • atomic no goes down by 1 but mass doesnt change
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26
Q

what happens when a neutron is ejected from a nuculeus?

A

mass no goes down by 1 but atomic number doesnt change

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27
Q

what happens in gamma radiation to make the nuclei more stable?

A

subatomic particles in nucleys re-arrange

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28
Q

what does a nuclear equation show?

A

what happens during radioactive decay

29
Q

what are the rules of nuclear equations?

A

must be balanced - total mass number must be the same on each side and charges must be the same

30
Q

how to find isotope remaining from half lifes?

A
  • find out how many times the thing has halved its life
  • times that by the original mass
31
Q

what defines the activity of any radioactive substance + how is it measured?

A

number of nuclear decays per second - measured in becquerels (Bq)

32
Q

what is half life?

A

time taken for half the unstable nuclei in a sample to decay

33
Q

What can radioactivity be used for?

A

killing micro-organisings
radioactive detecting
Cancer
checking thinkness of paper
smoke alarms

34
Q

give 2 examples of how killing microorgnisms is an example of using radioactivity?

A

Food can be irridated with gamma rays to kill bacteria making it safer to eat

Surgicl instruments need to be sterilised to kill microorganisms - also done by gamma rays

35
Q

give an example of how radioactive detecting is an example of using radioactivityin every day life

A

gamma source added to water detect leaks in water pipes underground via a GM tube that will detect higher radiation where there is a leak

36
Q

give an example of how cancer is an example of using radioactivity

A

used to help diagnose cancer using tracers in the body that can also be used to treat cancer

37
Q

give an example of how checking thickness of paper is an example of using radioactivity

A

Detector counts the rate at which beta particles get through from a source on one side - thickness will be determined by how many get through (more = thinner)

38
Q

give an example of how smoke alarms is an example of using radioactivity

A

contains a source of alpa particles - source releases these which ionise air molecules which are now attracted to plates with an opposite charge and allow current to flow - this is slowed when smoke gets into the gap and the alarm sounds

39
Q

Name 3 types of dangers of radioactivity?

A

Handling radioactive source, Radiation in hospital, nuclear accidents

40
Q

why is radioactivity dangerous?

A

a large amount of ionising radiation can cause tissue damage such as reddened skin and un-seen effects such as damaging the DNA inside of a cell (mutation) which can cause a cell to malfunction

41
Q

how can dangers of radioactivity be minimised when handling radioactive sources?

A

The intensity of radiation decreases with distance from the source - so, holding with tongs increases distance, therefore decreasing radiation intensity

42
Q

how can dangers of radioactivity be minimised with radiation in hospital?

A

exposure limited by increasing distnace, shielding the source + minimising time spent in present of source. Their exposure is closely monitored with dosimeter badges

Patients exposure is minimised by using the smallest dose of radiation possible with sources that have the shortest half lives to minismise time of exposure

43
Q

What is irridation? how do you classify someone as ‘irridated’?

A

someone is irridated when exposed to any source if radiation from nearby radioactive mentals. Once they move away, the irridation stops. I rridation is temporary.

44
Q

what is contamination? how can you define a person as being ‘contaminated’?

A

someone becomes contaminated if they get particles of radioactive material on their skin / inside their body. The exposure only stops when all material has decayed or source is removed.

45
Q

why are contamination from materials with longer half lives pose a bigger threat than those with short ones?

A

because the effect lasts longer

46
Q

How are gamma rays used to diagnose medical conditions?

A

A radioactive tracer that emits gamma rays is placed inside a patient - the location of it can be followed using a gamma camera

47
Q

what are gamma tracers used to find? how do they do this?

A

find sources of internal bleeding - gamma cameras detect the area of highest gamma radiation which is where bleeding occurs

dectect tumors - tracer made of radioactive glucose molecules because active cells like cancer cells take up glucose quicker than other cells

48
Q

how are positrons used to diagnose medical conditions?

A

tracer emits a positron - when this meets an electron - the positron and electron are destroyed and 2 gamma rays are emited in opposite directions. Detector in PET scanner moves around pateint to build up a set of images showing where different amounts of gamma radiation come from

49
Q

Why do the radioactive isotopes used in medical tracers need to have short half lives?

A

so that other parts of the body are affected as little as possible

50
Q

how does internal radiotherapy treat cancer?

A

cancer cells divide more rapidly than most cells in body so are more suseptiable to radiation. internal radiotherapy uses a better emiiter placed in the body close to a tumor in hopes of killing it.

51
Q

How does external radiotherapy treat cancer?

A

uses beams of gamma rays/X-rays/protons directed at tumor from outside body to try kill it

52
Q

what 2 types of nuclear reaction that are used as a source of energy on a large scale?

A

nuclear fission and nuclear fusion

53
Q

what is nuclear fission? - where is this nuclear reactio used?

A

large nuclei break up to form 2 smaller nuclei and release energy - used in nuclear power stations

54
Q

what is nuclear fusion and where is this type of nuclear raction used?

A

2 small nuclei join together to form a large nucleus. Fusion reactions release energy inside the sun+ stars

55
Q

What makes nuclear fuels useful for naval ships / submarines?

A

stores a lot of energy per kiolgram than any other type of fuel and they do not burn so they do not need air to allow them to release enrgy and dont produce CO2

56
Q

Why are nuclear energies useful in power stations?

A

supplies last longer than other non-renweable sources of energy

57
Q

What are the draw backs of nuclear energy?

A

radioactive waste in produced - expensive to treat.
Makes part of nuclear power station become radioactive - is expensive to dismantle at the end of station’s life

58
Q

What happens in nuclear fission? (detail)

A

when a large nuclei absobs a neutron it immediately splits into 2 smaller daughter nuclei that are radioactive + 2 or more neutrons also released. All products of the large nuclei store lots of kinetic energy as are moving at high speeds - energy is also transfered by heating. If a nuetron released is absorbed by another large nuclei - the chain reaction continues

59
Q

how can the nuclear chain reaction in nuclear fission be controlled?

A

if other materials absorb the neutrons produced by fission

60
Q

how is a nuclear reactor put together?

A

fuel rods are made from nuclear fuel, then inserted into holes in a material called a moderator to slow down neutrons, control rods are added inbetween fuel rods to control the chain reacton / temper the rate of fission

61
Q

how do nuclear reactors produce electricity?

A
  • energy is released from the core of the reactor and transfered to a coolant (water) -
  • then pumped through the reactor.
  • Hot coolant is pumped to a heat exchanger where it is used to make steam
  • steam drives the turbine that turns a generatetor to produce electricity
62
Q
A
63
Q
A
64
Q
A
65
Q
A
66
Q

what reaction is the main energy source for stars?

A

fusion reactions in which hydrogen nuclei combine to form helium

67
Q

What is electrostatic repulsion?

A

The protons in nuclei are positively charged. Charges which are the same will be replled

68
Q

How does the sun allow nucleur fussion to take place?

A

to fuse, nuclei need to get extremely close to eachother. The sun has a strong gravitational field which creates extremely high pressures in its centre which force nuclei to be very close together and hence are more likely to collide - especially with higher temperatures and travelling at a faster rate. This allows them to overcome electrostatic repulsion and fuse

69
Q

Why can we not achieve nuclear fusion?

A

we could not recreate a high enough pressure on earth and to speed up the particles enough to collide at a higher rate than the sun - we woukd have to raise the temperatures to be hotter than inside the sun. (yikes)

physics (41 decks)

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