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radioactivity Flashcards

1
Q

what are atoms

A

building blocks of all matter

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2
Q

what do atoms have in the centre

A

nucleus with electrons orbiting around it

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3
Q

protons

A

positively charged particles with a relative atomic mass of one unit

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4
Q

neutrons

A

no charge, and has a relative atomic mass of one unit

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5
Q

electrons

A

negative charge with almost no mass

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6
Q

ionised

A

if an atom loses electrons

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7
Q

atomic number

A

number of protons in an atom

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8
Q

mass number

A

total number of particles in the nucleus of an atom

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9
Q

isotopes

A

atoms of the same element that have the same number of protons but a different number of neutrons

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10
Q

why are isotopes unstable

A

due to imbalance of protons and neutrons

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11
Q

what do unstable nuclei emit

A

radiation to become more stable

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12
Q

forms of radiation

A

high energy particle
wave

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13
Q

radioactive decay

A

process of emitting radiation

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14
Q

what process is radioactive decay

A

random process

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15
Q

nuclear radiation

A

when an unstable nucleus decays it emits radiation

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16
Q

types of radiation

A

alpha
beta
gamma

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17
Q

alpha particles

A
  • helium nucleus
  • 2 protons and 2 neutrons
  • charge of +2
  • can be affected by an electric field
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18
Q

beta particles

A
  • fast moving electrons
  • produced in nuclei when a neutron changes into a proton and electron
  • charge of -1
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19
Q

gamma rays

A
  • EM waes
  • highest energy of EM waves
  • no charge
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20
Q

range in air- alpha

A

few cm

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21
Q

beta- range in air

A

few 10s of cm

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22
Q

range in air- gamma

A

infinite

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23
Q

alpha penetration and ionisation

A

stopped by paper
high

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24
Q

beta penetration and ionisation

A

stopped by a few mm aluminium
medium

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25
gamma penetration and ionisation
REDUCED by few mm of lead low
26
alpha decay
mass number decreased by 4 atomic number decreased by 2
27
beta decay - explanation
- neutron changes to proton and e- - electron is emmitted - proton remains in nuclei - completely NEW element formed
28
beta decay
mass no. remains the same atomic no. increased by 1
29
gamma decay
mass and atomic number stays the same
30
neutron emmision
atomic no. no change mass number decreases by 1
31
amount of radiation received by a person
dose measured in seiverts
32
how to detect and measure radiation
using photographic film GM tube
33
photohraphic flim
becomes darker when absorbing radiation.
34
GM tube
transmits an electrical pulse to a counting machine each time it absorbs radiation
35
count rate
clicking sound GM tube displays - the greater the clicks, the more radiation absorbed
36
background radiation
the radiation that exists around us all the time
37
background radiation stats
radon gas- 50% rocks and building materials- 15% medical- 13% food- 11% cosmic rays- 10% other- 1%
38
natural sources of radiation
rocks cosmic rays from space food
39
man made sources of radiation
- nuclear weapons - exposure from medical testing
40
what decays into radon gas
uranium
41
cosmic rays from space
- sun emits protons - enters atmosphere at high speed - collide with air molecules
42
carbon-14
- organic matter contains this
43
radiactive activity
the rate at which the unstable nuclei from a source of radiation decays
44
what is activity measured in
becquerels (Bq)
45
decreasing activity
- decreases with time
46
half life
the time it takes for the number of nuclei of a sample of radioactive isotopes to decrease by half
47
how to calculate half life
- meausre original activity - determine half-life of original - measure how activity changes over time
48
smoke detectors
- alpha radiation normally ionises the air creating a current - alpha emitter is blocked when smoke enters - alarm is triggered by a microchip when the sensor no longer detects alpha
49
what is used to measure the thickeness of thin materials
beta particles
50
why is beta particles used to measure thickness
- partially absorbs the material
51
why cant alpha be used to measure thickness
all of the particles would be absorbed and none would get through
52
radiotheraphy
treatment of cancer using radiation
53
radiotheraphy method
- gamma rays directed at cancerous tumour - tracer used to track movement of substances in blood - PET scan detect emissions from tracer to diagnose cancer and determine location
54
why is gamma used to sterilise
- most penetrating - irradiate all sides - can sterilise without removing packaging
55
contamination
unwanted presence of materials containing radioactive atoms on other materials
56
common cause of contamination
radiation leak
57
irradiation
process of exposing a material to radiation
58
why is irradiation harmful
kills living cells
59
what is irradiation used for
method of sterilising
60
source of irradiation
danger is from radiation emmitted OUTSIDE the object
61
prevention of irradiation
using shielding such as lead clothing because it abosrbs radioactive material
62
source of contamination
radiation emitted WITHIN the object
63
prevention of contamination
prevented by safe handling of sources and air tight safety clothing because it prevents atoms from getting inside
64
radiation on living cells
causes mutations or can kill cells, can from tumours
65
acute radiation exposure
skin burns, reduce WBCs
66
handling material
use tongs wear protective clothing shielding limit time used for
67
disposure of radioactive waste
buried underground to prevent being released to environment

Physics (6 decks)

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