Radioactivity Flashcards
3 types of radiation
Alpha
Beta
Gamma
What is irradiation
Being exposed to ionising radiation
What is contamination
Unwanted presence of radioactive nuclei on/ inside body
What does radiation dose measure
The health risk of exposure to radiation. Depends on type and amount of radiation
What does radiation dose depend on
Amount and type of radiation
Facts about alpha radiation
2 protons, 2 neutrons
Charge of +2
High ionising power
Can be blocked/ absorbed by paper and dead skin cells
Can travel a few cm in air
Away from you isn’t dangerous (doesn’t travel far and can be blocked by skin)
Inside you is dangerous due to high ionising power
Alpha decay occurs when a particle with 2 protons and 2 neutrons (helium nucleus) is released from the nucleus
Facts about beta radiation
1 electron
Charge of -1
Can travel a few metres in air
Blocked/ absorbed by a few mm of aluminium
Medium ionising power
Beta decay occurs when a neutron turns into a proton which creates an electron that’s emitted from the nucleus
Facts about gamma radiation
It is an electromagnetic wave
It has no charge
It can travel a few km in the air
It can be blocked/ absorbed by a few cm of lead
It has a low ionising power
It is the most dangerous radiation outside of your body because it can travel the furthest and takes a few cm of lead to be blocked but inside of you it’s the least dangerous as it has the lowest ionising power
Gamma decay occurs when the nucleus releases energy in the form of an electromagnetic wave (photon) e.g during nuclear fission process
What is alpha decay
Particle with 2 protons and 2 neutrons released from the nucleus
(What’s released is the same as a helium nucleus)
What is beta decay
Neutron turns into proton which creates an electron that’s emitted from the nucleus
What is gamma decay
Nucleus releases energy in form of electromagnetic wave (photon)
What is the type of electromagnetic wave called in gamma radiation
Photon
Which type of radiation is most dangerous inside body
Gamma- has highest ionising power
Why is alpha radiation the most dangerous when in the body
Has highest ionising power
Why is alpha radiation not very dangerous outside of the body
Can only travel a few cm in air
Is blocked by dead skin cells
Which type of radiation is most dangerous outside of body
Gamma
Travels a few km in air
Requires a few cm of lead to be blocked
Which type of radiation is least dangerous inside the body
Gamma- has lowest ionising power
What can each type of radiation be blocked/ absorbed by
Alpha- paper/ dead skin cells
Beta- a few mm of aluminium
Gamma- a few cm of lead
What is meant by activity
Rate at which source of unstable nuclei decays
(Measured in Bq)
What is meant by Count rate
Number of decays recorded each second by a detector
(Measured in a Bq)
Example of detector used to measure count rate
Geiger-Muller tube
3 uses of radioactivity
Medical traces, automatic thickness monitoring, radiotherapy
What is meant by hale life of radioactive isotope
Average time for half of unstable nuclei to decay/ for activity of source to half
The activity of a radioactive source decreases….
Exponentially
How can a radioactive substance become more stable
Unstable nuclei decay (emit ionising radiation)
True or false, background radiation is around us all the time
True
Examples of background radiation
Natural sources- rocks, food, animals, cosmic rays
Man-made sources- nuclear weapons and nuclear accidents
Natural sources of background radiation
Food, cosmic rays, rocks, animals
Manmade sources of background radiation
Nuclear weapons and nuclear accidents
What is nuclear fusion
Joining of 2 smaller atomic nuclei to form 1 larger one
During nuclear fusion some of the mass of the nuclei is converted into energy therefore the larger nuclei has a lower overall mass
During nuclear fusion why does the larger nuclei have a lower overall mass
During the process some of the mass of the smaller nuclei is converted into energy
What is formed from the 2 smaller nuclei in nuclear fusion
1 larger nuclei with a lower overall mass (some mass of the smaller ones is converted to energy)
What is nuclear fission
Splitting of an atomic nucleus
Neutron gets absorbed by a fissionable nucleus, nucleus breaks apart into 2 daughter nuclei and releases 2-3 neutrons + energy in the form of gamma rays
Process of nuclear fission
Fissionable nucleus absorbs a neutron
Nucleus becomes unstable and splits into 2 daughter nuclei
Energy released in form of gamma rays + 2-3 neutrons released
What does a fissionable nucleus absorb in nuclear fission
A neutron
After 2 daughter nuclei are formed what else is released in nuclear fission
2-3 neutrons
Energy in form of gamma rays
Do irradiated objects become radioactive
No, they are just exposed to the radiation
Do contaminated objects become radioactive
Yes
Which out of contaminated and irradiated objects become radioactive
Contaminated
Briefly explain how automatic thickness monitoring works (a way of thinning metal to make aluminium foil)
Beta radiation is absorbed by the aluminium
Thicker aluminium means more beta radiation absorbed so lower count rate
Thinner aluminium means less beta radiation absorbed so higher count rate
Detector of count rate works out how thin/ thick it is
Type of radiation absorbed by aluminium in automatic thickness monitoring process
Beta
Briefly explain how radiotherapy works
Radiation treats tumours by killing targeted cancer cells
Beams fired from multiple angles so only target gets high dose
Uses gamma rays
Radioactive traces show flow through an..
Organ
Why is rolling dice a suitable model for radioactive decay
Both are random processes
Why when sample of radioactive material is placed by a detector the count rate is lower than teh activity
Not all radiation emitted by sample is detected by the detector
As Some radiation is absorbed before it reaches the detector
Why when sample of radioactive material is placed by a detector the count rate is lower than teh activity
Not all radiation emitted by sample is detected by the detector
As Some radiation is absorbed before it reaches the detector
What can be determined about radioactive sources A and B if A has a greater half life
Nuclei in source A are more stable than in source B
(Nuclei in source A are less likely to decay than nuclei in source B in given time period)
What happens to mass number and atomic number of radioactive substance that emits beta radiation
Mass number stays the same
Atomic number increases by 1 (as neutron turns into proton)
What happens to mass number and atomic number of substance that emits alpha radiation
Mass number decreases by 4 and atomic number decreases by 2
(As particle containing 2 portions and 2 neutrons is emitted)
Why is dice a good model for the RANDOM nature of radioactive decay
We cannot predict when the dice will decay
We cannot predict which dice will decay
Key word used when describing why beta and gamma radiation are dangerous when outside of the body
They can PRNETRATE into tissues and increase the risk of cancer
What controls the chain reaction of nucleus fission in power stations
Control rods which are lowered to absorb the released neutrons
What is spontaneous fission
Where unstable nucleus splits apart without absorbing a neutron
Name for process where unstable nucleus splits apart without absorbing neutron
Spontaneous fission
Name for uncontrolled chain reactions
Nuclear explosions
Why teacher stands far away from apparatus when using radioactive slice that emits gamma radiation
To reduce radiation to reduce risk of cancer as gamma radiation is ionising and increases the risk of cancer
Example of nucleus used in nuclear fission
Uranium 235
When absorbs neutron becomes uranium 236 so is very unstable and splits into 2 daughter nuclei
What type of radiation is used in smoke detectors
Alpha
