Radiation

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Ionisation
-results in an atom becoming an ion which is a charged particle -if an ion loses a negative electron it becomes a positive ion -can occur due to radioactive particles or waves
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Ionisation (definition)
-the gain or loss of electrons from an atom - turns atoms into charged ions
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Radioactive Particles and Waves
-are emitted from the nucleus of an unstable atom -three types, alpha, beta & gamma
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Alpha Radiation
-made up of 2 protons and two neutrons, same structure as a helium nucleus - they have the highest ionisation density - absorbed by a few cm of air or a sheet of paper - radiation weighting factor 20
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Beta Radiation
-fast moving electron ejected from the nucleus -result in a neutron becoming a proton -low ionisation -absorbed by a few mm of aluminium -radiation weighting factor is 1
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Gamma Radiation
-high energy EM wave -low ionisation -absorbed by several cm of lead -radiation weighting factor is 1
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Background Radiation
-comes from: cosmic rays, the human body, radon gas and from rocks, soil and buildings
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Activity
-A -number of nuclei in a radioactive substance which decay every second -measured in becquerels (Bq) -activity of a source decays with time as the number of radioisotopes in the source decrease -equation A=N/t N=At t=N/A
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Half Life
-is the time it takes for the activity of a source to decrease by half
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Absorbed Dose
-D -is the energy absorbed per kg of tissue from radiation -measured in grays Gy -equation D=E/m, E= Dm, m=E/D -1 Gy means 1 joule has been absorbed per kg 1Gy= 1Jkg-1
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Radiation Weighting Factor
-given to each type of radiation as a measure of it biological effect or damage it may cause -how harmful the radiation is to biological material
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Equivalent Dose
-measures the biological harm radiation has on living things -measured in Sieverts Sv -equation: H = DWR WR=H/D D= H/WR
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Equivalent Dose Rate
-H with dot-measures the rate at which radiation is absorbed by biological material to prevent overexposure to radiation -measured in Svh-1 or Svyear-1 or other - H with dot = H/t
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Measuring Half life
-background counts must be found first then taken away from the counts with the source present to find the corrected count rate -a graph of corrected count rate against time is then plotted
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Nuclear Fission
-used in nuclear power stations -releases energy-occurs when a large nucleus splits into smaller nuclei -happens in two ways, induced or spontaneous
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Spontaneous Nuclear Fission
-is a random event and occurs naturally
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Induced Nuclear Fission
-nuclear fission is induced by neutron bombardment -neutron are emitted and energy is released
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Nuclear Fusion
-the joining of two smaller nuclei to form a larger nucleus -releases energy -is the process by which stars produce heat
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Chain Reaction
-when the neutrons released from a fission reaction split subsequent nuclei and the process continues until you run out of nuclei that can be split
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Uses of radioactivity
-to sterilise medical equipment -gamma rays can be used in radiotherapy (cancer treatment), source must emit gamma as it is the only type that can pass through the human body
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Medical Tracer (use of radioactivity)
-can be injected or swallowed into the body to allow images of the inside to be created and find blockages, must emit gamma rays as these can pass in and out of the body
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Film Badge
-indicates the amount of radiation received by the darkness of the film -can indicate what type of radiation is received by what area of the film is affected.
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Fusion Reactors
-are hard to achieve on earth due to the repulsive nature of the positive nuclei -temperatures in order of 10^8K are required to stimulate the fusion reaction which takes place in our sun
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Fusion Plasma
-containment is a problem because the very high temperature of the plasma will melt most materials -contained using magnetic fields
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Biological harm due to radiation depends on:
-type of radiation -type of tissue -absorbed dose
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Application of alpha
-smoke detectors
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Application of beta
-monitoring paper thickness
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Application of gamma
-radiotherapy/medical tracers
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Other cards in this set

Card 2

Front

-the gain or loss of electrons from an atom - turns atoms into charged ions

Back

Ionisation (definition)

Card 3

Front

-are emitted from the nucleus of an unstable atom -three types, alpha, beta & gamma

Back

Preview of the back of card 3

Card 4

Front

-made up of 2 protons and two neutrons, same structure as a helium nucleus - they have the highest ionisation density - absorbed by a few cm of air or a sheet of paper - radiation weighting factor 20

Back

Preview of the back of card 4

Card 5

Front

-fast moving electron ejected from the nucleus -result in a neutron becoming a proton -low ionisation -absorbed by a few mm of aluminium -radiation weighting factor is 1

Back

Preview of the back of card 5
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