Radiation Flashcards
(36 cards)
What is carbon dating
Uses isotope carbon 14. It is used to find out how old something is
How does carbon dating work
Only works for materials that were once living. Living organisms take in carbon 14 but when they die the replacement process stops. Carbon 14 has a half life of 5600 years, so we can work out how long ago something e.g a tree died by comparing the amount of carbon 14 left in it to with how much would be in a similar living organism.
What are possible problems with carbon dating
Assumes the level of cosmic radiation reaching the earth is constant . Also inorganic living matter e.g rocks and minerals does not absorb carbon 14
What is carbon 14
Made when high energy neutrons collide with nitrogen atoms . The high energy neutrons are formed when cosmic rays cause atoms in the atmosphere to break up
How do we date radioactive rocks
Inorganic matter and non living matter does not absorb carbon 14 we need to use other elements to date them. When a radioactive isotope decays, the original isotope is called the parent nuclei. If the products of decay also decay we get a decay series , at the end of this we have a stable isotope. In a rock the proportion of parent to stable daughter nuclide gives a measure of the age of the Rock
How can we product radiographer a
Monitor their exposure to radiation and make sure they handle it from a safe distance
How can we store nuclear waste
In sealed lead containers capable of holding radiation for enormously long periods of time
What is the nucleus of an atom
Contains protons and neutrons and make up the mass of the atom
What is the atomic number
Total number of protons , elements are ordered in this order
What is the mass number
Protons + neutrons
What are isotopes
Many elements have a few different isotopes. Isotopes are atoms with the same number of protons (atomic number) but a different number of neutrons ( different mass number). Usually each element has only one of two stable isotopes like carbon 12. The other isotopes tend to be radioactive , the nucleus is unstable so it decays and emits radiation
How does radioactive decay work
Random. Unaffected by physical conditions .when the nucleus does decay it splits out one or more of three different kinds of radiation - alpha , beta and gamma. In the process the nucleus often changes into s new element
What is background radiation
Low level background nuclear radiation around us all the time comes from : substances on earth e.g food air building materials soil rocks
Radiation from space (cosmic rays )that come mostly from the sun
Living things
Radiation due to human activity e.g fallout from nuclear explosions or nuclear waste
What is ionisation
Nuclear radiation causes ionisation by bashing into atoms and knocking electrons off them. Atoms are turned into ions. The further the radiation can penetrate before hitting an atom the less damage it will do so a less ionising
What are alpha particles
2 protons and 2 neutrons . Big heavy slow moving. Don’t penetrate far into materials but are stopped quickly. Because of their size they are strongly ionising , which means they bash into a lot of atoms and knock electrons off them before they slow down , which creates lots if ions . They’re electrically charged (positive) they can be deflected by electric and magnetic fields. Emitting an alpha particle decreased the atomic number by 2 and the mass number by 4
What are beta particles
An electron which had been emitted from the nucleus of an atom where a neutron turns into a proton and an electron . When s beta particle is emitted the number of protons in the nucleus increase by 1 (atomic number ) but the mass number stays the same. The move quite fast and are quite small. Penetrate moderately and are moderately ionising . Because they’re negatively charged they can be deflected by electric and magnetic fields
What are gamma rays
Short wavelength electromagnetic waves. They’re just energy. Can penetrate a long way into materials without being stopped but this means they are weakly ionising as they tend to pass through atoms instead of colliding but when they hit something they do damage. They have no charge and are not deflected by electric or magnetic fields . Gamma emission happens after beta or alpha decay. Has no effect on mass or atomic number of atom it is just the nucleus emitting excess energy in the form of a gamma ray
What are the radiation blocked by
- alpha particles blocked by paper skin , few cm of air
- beta particles stopped by thin metal
- gamma rays blocked by thick lead or very thick concrete
How can gamma rays be used to treat cancer
Gamma source is moved around the body of the patient so that the rays go through the cancer cells but go through a different part of the healthy tissue each time to keep the damage of the healthy cells down to a minimum
How is radiation used in sterilisation
Because radioactive radiation destroys cells it can be used to destroy bacteria . Food or medical instruments do not need to be taken out of their packaging - the radiatiOn will pass through it and destroy the harmful organisms inside.
How can radiation be used in thickness and measurement control
Radioactive source emits beta particles which can pass through the metal , the thicker the metal the more beta particles there are absorbed so the lower the reading on the detector . For thin sheets more beta particles get through so the reading on the detector is higher. By first using carefully measured thickness of metal the correct reading on the meter is recorded and marked on the scale if the reading is above the scale , the metal is too thin if it is below the scale it is too thick. The meter is usually coupled to the machine which controls the rollers and as its readings change it adjusts the rollers so that the sheet of metal is produced at the correct thickness
How can we measure radiation
Photographic film or Geiger muller detector
How are radioactive tracers used
Radioactive fertilisers can be fed to plants and then traced through the plant using a Geiger muller counter . This is used to delevop better fertilisers and incesticides. Similarly in hospitals and isotope with a short half life is injected into a patients body . A gieger muller counter is used to trace the movement of the chemical through the patients body , to check that certain glands are functioning properly. Tumours can be located beachside they take up more radioactive isotope than other parts of the busy
How can means from a pipeline be detected
Inject a radioactive isotope into the pipeline so leaks can be detected
