Radioactivity Flashcards
In nuclear notation, what is the top number and what is the bottom number?
- Top number is the mass number (no. of protons + no. of neutrons)
- Bottom number is the atomic number which determines the element (no. of protons)
Unless it is an ion, the number of protons will be equal to the number of electrons
What does ionisation mean?
The gain or loss of electron(s) in order to form an ion
What is an isotope?
An atom with the same number of protons but a different number of neutrons
Isotopes occur naturally, but some are more rare than others
Why do some nuclei emit radiation?
- Because they are unstable as they are isotopes which are too big and/or have too many or too few neutrons
- They emit radiation to become more stable
Radioactive decay is a random (unpredictable) process
What are the three types of nuclear radiation that can be emitted from unstable nuclei?
- Alpha
- Beta
- Gamma
What does an alpha particle released from an unstable nucleus consist of?
Two protons, and two neutrons (+2 charge)
It is the same as a helium nucleus
What does a beta particle released from an unstable nucleus consist of?
One electron (-1 charge)
What does gamma radiation released from an unstable nucleus consist of?
High energy electromagnetic waves (gamma rays)
Gamma rays have no charge so cannot be affected by electromagnetic fields
What is the order of penetrating power between the three types of radiation?
Gamma - High (Stopped by 1m of concrete)
Beta - Medium (Stopped by 1cm of Aluminium)
Alpha - Low (Stopped by paper)
Same goes for range and speed
What is the order is ionising ability between the three types of radiation?
Alpha - High
Beta - Medium
Gamma - Low
Because alpha radiation has the highest mass, size charge etv. This obviously ties in with penetrating power too
What is the order of mass and size between the three types of radiation?
Alpha - High
Beta - Low
Gamma - N/A
When measuring the radioactivity of a source, what property should it have for reliable results?
Long half life
What must you take into consideration when measuring the count rate of a source?
The background radiation
When is the effect on a nucleus when it emits an alpha particle?
- The mass number decreases by four
- The atomic number decreases by two, so a new element will be formed
- The charge decreases by two
What is the effect on a nucleus when it emits a beta particle?
- A neutron is turned into a proton and an electron, the proton is kept and the electron is emitted
- The mass number stays the same, but the atomic number increases by 1, forming a new element
- The charge increases by 1
What is the effect on a nucleus when it emits gamma radiation?
There is no effect on the nucleus, however it does become less energetic
What are the two devices you can use to measure radiation?
- Geiger-Muller Tube/Detector
- Photographic film
What are the natural sources of background radiation?
- Radon gas from radioactive rocks like granite
- Other rocks and soil which emit radiation
- Radioactive cosmic rays from the sun
- Radioactive material in food and drink like potassium-40 in bananas
- Radiation from carbon-14 in all living materials
What are the man-made sources of background radiation?
- Medical uses, like x-rays and radiation therapy
- Fallout from nuclear weapon testing
- Nuclear waste and nuclear accidents from power stations
What unit is radioactivity measured in?
(The rate at which unstable nuclei decay)
Bequerels (Bq)
What happens to the activity of a radioactive source overtime and why?
- It decreases
- This is because each decay reduces the overall number of radioactive particles in the source
What is the definition of half life?
The time it takes for the number of nuclei/actvity in a sample of a rdioactive sample to decrease by half
- Half life is different for every isotope because the rate of decay (actvity) is different
- Sources with short half lives tend to have higher activities
How does a smoke detector work?
- A source is placed in the detector, usually alpha and with a long half life as it cannot penetrate the casing of the detector and will ionise the air
- There will be a current detector as well
- If smoke enters the detector, the alpha particles will no longer ionise the air as it will be blocked and there will no longer be a current present
- The drop in current will sound the alarm
It might also be done with a radiation detector, and if a drop in count rate is detected due to the blocking smoke, an alarm will sound
How can radiation be used to measure thickness of paper/foil in industry?
- Beta should be used, as it will penetrate the paper, but not penetrate everything including the counter
- If the thickness of the paper changes, the count rate changes
- The source should have a long half life to achieve a constant reading
How are radioactive sources used in medical tracers?
- A radioactive source will be injected into a patient
- A radiation detector can measure the activity of the source when inside the body, finding diagnostics like the location of tumours
- It should be gamma so it can penetrate the body and does not ionise, and should have a short half life so the patient suffers little exposure
How can radiation be used in radiotherapy?
- Precise beams of gamma radiation are fired at cancerous tumours, while minimising damage to healthy cells
- Gamma rays are used as they can penetrate the whole body
How can radiation be used to sterilise food and medical equipment?
- The item is irradiated with gamma radiation to kill bacteria
- It is gamma so that it penetrates the whole item including its packaging and still kills the bacteria
What is contamination?
- The unwanted presence of materials containing radioactive atoms
- This will make the material itself radioactive
What is irradiation?
- The process of exposing a material to a specific source of radiation
- The material itself does not become radioactive, but it can kill living cells on the material
What are the dangers of radiation?
- DNA damage/mutation from ionisation, causing cancers and tumours
- Cell and tissue damage, like skin burns, white blood cell damage etc.
What are the problems with disposing of nuclear waste and how can the risks be reduced?
- The radioactive sources can have a long half life and can contaminate areas around it
- They should be buried deep undergroud, sealed by lead or concrete
How can you reduce the risk to your health from radiation?
- Store sources in a lead-lined container with shielding
- Increase the distance from you and the source by using tongs
- Reduce time exposed to the source
- Avoid contact with bare skin and wash yourself after being around it
- Protective clothing should be worn, like lead-lined apron
