Atoms and Nuclear Radiation Flashcards
Define radioactive decay.
Some atomic nuclei are unstable. Radioactive decay is where these give out radiation as they change to become more stable.
What is activity, and which unit is it measured in?
Activity is the rate at which a source of unstable nuclei decays, measured in becquerels (Bq).
What is count rate?
Count rate is the number of decays recorded each second by a detector such as a Geiger–Müller tube.
Explain the 4 types of nuclear radiation.
- An alpha particle is equivalent to a helium nucleus.
- A beta particle is a high speed electron ejected from the nucleus as a neutron turns into a proton.
- A gamma ray is EM radiation emitted from the nucleus.
- A neutron is self-explanatory.
Compare the penetration through materials, range in air, and ionising
power of alpha particles, beta particles and gamma rays.
Gamma is most penetrating, gamma travels furthest in air, alpha is most ionising.
What is the half-life of a radioactive isotope?
The half-life is the time it takes for the number of nuclei of the isotope in a sample to halve, or the time it takes for the count rate (or activity) from a sample containing the isotope to fall to half its initial level.
Define radioactive contamination.
Radioactive contamination is the unwanted presence of radioactive atoms on materials. The hazard from contamination is due to the decay of the contaminating atoms.
Define irradiation.
Irradiation is the process of exposing an object to nuclear radiation. The irradiated object does not become radioactive.
Explain sources of background radiation.
Natural sources include rocks and cosmic rays from space. Man-made sources include fallout from nuclear weapons testing and nuclear accidents.
Give 2 uses of nuclear radiation in medicine.
- Exploration of internal organs.
- Control or destruction of unwanted tissue.
What is nuclear fission and how is it triggered?
Nuclear fission is the splitting of a large and unstable nucleus such as uranium or plutonium. Usually, the nucleus must absorb a neutron - spontaneous fission is rare.
What are the products of nuclear fission, and how may they result in a chain reaction?
The nucleus undergoing fission splits into two smaller nuclei, roughly equal in size, and emits two or three neutrons alongside gamma rays. These neutrons can be absorbed by other nuclei, causing a chain reaction. All products have kinetic energy.
What is nuclear fusion?
Nuclear fusion is the joining of two light nuclei to form a heavier nucleus. In this process some of the mass may be converted into energy.
