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Yr 13 Physics 10 - Nuclear Radiation > Nuclear Radiation > Flashcards

Nuclear Radiation Flashcards

1
Q

what is background radiation

A
  • low level radiation from environmental sources

- always present around us

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2
Q

what are the units of the geiger-muller counter and counter

A

becquerels (Bq)

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3
Q

what makes 50% of background radiation

A

radon gas

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4
Q

what 4 other things make the big chunks

A
  • ground and building (14%)
  • medical (14%)
  • food and drink (11.5%)
  • cosmic rays (10%)
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5
Q

how is the radon gas produced

A

from the decay of uranium ore present in certain rocks

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6
Q

how would you properly measure the background radiation of your environment using a gm tube and counter

A
  • leave the gm tube and counter to count the background radiation over a recorded long period of time (30 mins)
  • divide the total counts, shown by the counter, by the number of seconds the counter was counting for
  • giving you the number of counts per second (Bq)
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7
Q

why do you record the background radiation over a long period of time

A
  • so a good average is calculate

- as the count rate would be temporarily higher or lower than normal at times

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8
Q

what is the usual reading youd get from this kind of experiment

A
  • 0.5Bq

- anywhere between 0.2 and 0.5 is common in the UK

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9
Q

is you were measuring the radioactivity of a specific substance using a gm tube and counter, how would you calculate the corrected count

A
  • measure the count rate of the background radiation around you
  • measure the count rate of the substance
  • subtracting the BGR from the count rate of the substance
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10
Q

what is radioactive / nuclear decay

A
  • the process of a nucleus’ structure being changed

- usually accompanied by the emission of a particle

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11
Q

what does the emitted particle have when it leaves the nucleus

A

kinetic energy

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12
Q

what do these radiation particles usually do

A
  • it will ionise particles in its path as it moves
  • losing a small amount of KE at each ionisation
  • when all the KE has been transferred, the particle stops moving
  • then is absorbed by the substance it is in at that moment
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13
Q

what are the three main types of nuclear radiation

A
  • alpha (a)
  • beta (b)
  • gamma (Y)
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14
Q

what material does alpha radiation find hard to penetrate

A
  • paper

- a centimeters of air

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15
Q

what material does beta radiation find hard to penetrate

A
  • 5mm thick aluminium

- a few meters of air

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16
Q

what material does gamma radiation find hard to penetrate

A
  • 5cm thick lead

- several meters of concrete

17
Q

what is an alpha particle, what is its charge and what its ionisation like

A
  • an alpha particle is a helium nucleus (2p 2n)
  • it has a charge of 2+
  • and it is highly ionising
18
Q

how many ionisations does an alpha particle cause in the air per millimetre

A

about 10k

19
Q

putting two and two together, why do alpha particles get absorbed so easily

A
  • because their high amount of ionisations means they lose their KE very quickly
  • therefore they get absorbed very quickly
20
Q

what is a beta particle, what is its charge and what its ionisation like

A
  • a beta particle is a high speed electron
  • it has a charge of 1- or 1+
  • and its moderately ionising
21
Q

how is a b- particle formed

A
  • when a neutron decays into a proton

- and emits an electron (its negative charge)

22
Q

how is a b+ particle formed

A
  • when a proton decays into a neutron

- and it emits a position (its positive charge)

23
Q

why are b particle less ionising than a particles

A
  • because they are much smaller

- so they collide with and ionise particles less frequently

24
Q

what is gamma radiation, what is its charge and what is its ionisation like

A
  • gamma radiation is a type of high energy and frequency EM radiation
  • it has no charge
  • they are the least ionising of the three
25
Q

why are gamma rays the least ionising

A
  • because they have no charge or mass

- so they rarely interact with particles in their path

26
Q

if gamma rays have no mass or charge, what do they do to the nucleus when they are emitted

A
  • they transfer energy out of the nucleus

- causing the nucleus’ energy level to drop

27
Q

when does gamma ray emission usually occur from a nucleus and why

A
  • after beta or gamma decay

- because they usually leave the nucleus in an excited state

28
Q

in the experiment where we explore how much lead is needed to reduce the intensity of gamma radiation by a certain amount, a source that emits gamma and alpha radiation is used. what is the main setup point you need to remember

A

the distance between the source and counter must remain constant through out

29
Q

what else do you need to do in order to gain accurate results

A
  • place a sheet of paper in front of the source
  • to absorb the alpha radiation
  • as we only care about gamma
30
Q

what is done during this practical

A
  • place varying thicknesses of the lead plates in between the counter and source
  • for each thickness, record the count over a fixed period of time and work out the count rate
31
Q

what graph would be plotted

A

intensity of radiation (count rate) against thickness of lead

32
Q

what is the mathematical relationship between intensity and thickness of lead

A
  • I dpt e^(ux)
  • I = intensity
  • u = mu (i really dont know lol)
  • x - thickness of lead (m?)
33
Q

how dangerous is alpha radiation outside and inside the body

A
  • inside its very dangerous, causing radiation poisoning and cancer
  • outside its harmless, being absorbed by the surface layer of dead skin
34
Q

how dangerous is beta radiation outside and inside the body

A
  • inside its moderately dangerous, causing ionisation
  • outside is the same story
  • basically close exposure should be minimised
35
Q

how dangerous is gamma radiation outside and inside the body

A
  • inside its not too bad, long term exposure will cause cancer
  • outside its the same story
  • basically it causes minimal ionisation so dont stay around for long periods

Yr 13 Physics 10 - Nuclear Radiation (4 decks)

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