Paper 1 - Radioactivity And Particles Flashcards
What is the definition of Half-Life?
The time it takes for the count rate of a radioactive source to fall to half its original count rate
Describe the nature of alpha particles
- Stopped my air or paper
- Stronger affected by magnetic fields
- Heaviest particle
- Heavily charged
- Least penetrating power
- Most ionising
What is meant by atomic number?
The number of protons in the nucleus
Describe uses of radioactivity in medicine
- Gamma rays used to sterilise medical equipment
- Gamma rays can be used to target and destroy cancer cells
What happens to a radioactive source over time?
Activity (measured in Becquerels) decreases over time
What is meant by mass number?
The sum of the number of protons and neutrons in a nucleus
Describe the effects of neutron emission on the atomic and mass numbers of an atom
- Atomic number : no change
- Mass number : decreases by 1
Describe the structure of an atom in terms of protons, neutrons and electrons
- An atom has a nucleus containing protons and neutrons with an overall positive charge
- And gas orbital electrons, surrounding the nucleus in shells
What is background radiation?
- Radiation that is all around us at all times at a safe level
- Measured in Becquerels
- Includes alpha, beta and gamma radiation
What are the sources of background radiation and are they natural or artificial?
- Cosmic rays - natural
- Radon gas - natural
- Food and drink - artificial
- Nuclear weapon testing - artificial
- Nuclear power stations - artificial
- Medical - artificial
Describe the effects of Gramma emission on the atomic and mass numbers of an atom
- Atomic number : no change
- Mass number : no change
What is meant by isotope?
- Same number of protons
- Different number of neutrons
What can vary between different radioactive isotopes?
Half-Life
What is the difference between contamination and irritation?
- contamination is when a non-radioactive object comes into contact with a radioactive material
- irradiation is when radiation is present
Describe the effects of Beta emission on the atomic and mass numbers of an atom
- Atomic number : Increases by 1
- Mass number : no change
What are the issues with disposing of radioactive waste?
- Elements like Plutonium and Uranium have incredibly long half-lives and therefore will emit dangerous levels of radiation for a long term
- Which has an effect on plant and animal life
What are the dangers of ionising radiations?
- Radiation can cause mutation in living organisms
- Radiation can damage cells and tissues
- There are problems with the disposal of radioactive waste
Describe the nature of Gamma particles
- Most penetrative
- Least ionising
- Passes through aluminium but not lead
- Not a particle so has no charge or mass
- Pure energy
Describe uses of radioactivity in industry
- Can be used in smoke detectors
- Can be used in thickness detectors
- Can be used for nuclear weapons
- Can be used for radioactive tracers
- Can be used for leak detectors
What are alpha, beta and gamma rays?
Ionising radiations emitted from unstable nuclei in a random process
Describe the effects of Alpha emission on the atomic and mass numbers of an atom
- Atomic number - decreases by 2
- Mass number : decreases by 4
Describe the nature of Beta particles
- More penetrative than alpha, less penetrative than gamma
- Lighter than alpha
- Negative charge
- Stopped by aluminium or thin plastic
What can photographic film or a Geiger-Muller detector do?
Detect ionising radiations
What can nuclear reactions including fission and fusion be?
Sources of energy
How is a nucleus of Uranium-235 split?
- The process of fission
- Neutron collides with Uranium-235 atomic
- This releases energy as kinetic energy of the fission products
What does the fission of Uranium-235 produce?
- 2 radioactive daughter nuclei
- A small number of neutrons
How can a chain reaction be set up if the neutrons produced by one fission
strike other Uranium-235 nuclei?
In fission, a neutron from a previous decay can lead to more and more decays
Describe the role played by the control rods and moderator in the fission process
- Control rods soak up excess neutrons, preventing the chain reactions from getting out of control, otherwise, this could lead to a nuclear disaster
- The moderator functions to slow down the neutrons
What is nuclear fusion?
The creation of larger nuclei resulting in a loss of mass from smaller nuclei, accompanied by a release of energy
What is fusion the energy source for?
Stars
Explain why nuclear fusion does not happen at low temperatures and pressures, due
to electrostatic repulsion of protons
- At low temperatures/pressures, the positively charged protons will repel from each other
- When moving slowly, the particles do not have enough kinetic energy to overcome the electrostatic forces of repulsion so cannot fuse
Explain the difference between nuclear fusion and nuclear fission
- Fission is a chain reactions, Fusion is not
- Fusion is the joining of nuclei whereas Fission is the splitting of nuclei
What is the role of Shielding around a nuclear reactor?
To absorb hazardous radiation (daughter nuclei)
What are the products of the fission of uranium nuclei?
- neutrons
- daughter nuclei
- thermal energy
