Physics radioactivity Flashcards
What is an alpha particle?
2 protons, 2 neutrons
What is a beta particle?
An electron
What is a gamma ray?
Electromagnetic wave
Explain the difference between contamination and irradiation.
Contamination is when you actually contact the radioactive source. Irradiation is indirect exposure, when you are only contacted by the radiation.
What is a half-life?
The time it takes half the atoms to decay
How does a smoke detector (or fire alarm) work?
An alpha source constantly emits alpha particles, causing air particles to ionise. They become attracted to the oppositely charged metal plates, which creates a current. If smoke enters between the plates, it reduces alpha flow and thus ionisation and current, which triggers the alarm to sound.
How does automatic thickness monitoring use radiation?
Beta source placed above aluminuim foil, a detector and computer below it. The thinner the foil, the more particles get through, and vice versa. The amount of particles is detected by the detector, which passes information to the computer, which tells the rollers around the foil to give the it more or less space so that the thickness is right.
How can radiation be used as a tracer?
Pass a gamma source through the body. It will emit gamma rays to a detector outside the body. An abnormal amount of gamma emitted from certain parts of the body can reveal blockages.
How does radiotherapy work?
Beams of gamma rays are directed at cancerous tumours.
What is background radiation?
Ionising radiation that is constantly present around us.
Name 2 natural and 2 human sources of background radiation.
Natural: Cosmic rays from space, gamma rays from rocks and soil
Human: X-rays, total discharge from nuclear power industry
What 3 outcomes are possible if a cell’s nucleus is damaged by radioactive contamination?
The cell may die. The cell may accurately repair itself. The cell may misrepair itself and develop into a cancer.
Explain, in detail, how a uranium-235 atom is used to release energy through nuclear fission.
When a Uranium-235 nucleus absorbs a slow moving neutron, it becomes an unstable isotope and therefore splits into 2 daughter nuclei. At the same time it releases 2 or more neutrons, causing a chain reaction. The daughter nuclei have slightly less mass, which is converted into lots of kinetic energy.
What are the advantages of nuclear fission?
High energy density, long lifespan, no greenhouse gas emissions.
What is the disadvantages of nuclear fission?
Radioactive waste, expensive to build, must be placed in tectonic stability, risk of nuclear meltdowns.
Describe the differences between the plum pudding model and the nuclear model.
Nuclear model is mostly empty space, PP model is one large mass. Nuclear model has electrons orbiting instead of fixed in the PP model. Nuclear model has a nucleus in the center.
Your points must be put in pairs, stating the case for each model.
An atom of Iodine-131 decays into an atom of Xenon by emitting a beta particle. What will happen to the relative atomic mass and the charge of this atom?
Charge increases by 1 because it lost an electron.
Relative atomic mass has negligible change (same number).
An atom of Uranium-238 decays into an atom of Thorium by emitting an alpha particle. What will happen to the relative atomic mass and the charge of this atom?
Charge decreases by 2 because it lost 2 protons.
Relative atomic mass decreases by 4 because it lost 2 protons and 2 neutrons.
What is an isotope?
An atom of the same element but with a different number of neutrons in the nucleus so a different mass number.
