Chapter 21: Radiation Flashcards
How can ionising radiations be detected?
By photographic film: radiation imprints on camera film
By Geiger-Muller detector: A GM counter beeps in the presence of radiation. The more radiation, the more frequent the beeps.
What is the atomic number?
The number of protons in an element
What is the mass number?
The total number of protons and neutrons in the nucleus.
What is an isotope?
An element that has the same proton number, but a different neutron number
What are alpha and beta particles and gamma rays?
They are all types of radiation. They are ionising radiation that are emitted from unstable nuclei in a random process.
When does ionisation take place?
When radiation removes electrons from an atom. This required be radiation to do work, and therefore it transfers some energy to the ion pair.
What are features of alpha particles?
Alpha particles are two neutrons and two protons, also known as a helium nucleus.
Alpha particles are unable to penetrate a piece of paper.
What are features of beta particles?
They are electrons, and are emitted when a neutron turns into a proton and an electron.
They won’t penetrate aluminium.
What are features of gamma rays?
They are a type of electromagnetic wave, often emitted alongside the other types of radiation.
They cannot penetrate lead.
What are the sources of background radiation?
Radon gas from the ground, food and drink, cosmic rays, buildings and the ground, artificial sources like medical and nuclear power/weapons tests
What happens to radiation over time?
The radiation emitted by a radioactive source will decrease over time.
What is radiation measured in?
Becquerels, Bq
What is a half-life?
A half-life is the average time it takes for the radiation emitted by a source to decrease by half. Half-lives are different for different sources of radiation.
How is radioactivity used in non-medical tracers?
A radioactive source (beta or gamma) is put into a system. It will built up where there is a blockage, and be detected, showing where the problem is.
How is radioactivity used in medical tracers?
A radioactive source (gamma) is put into a body, and will build up at a blockage, so an area where there is a problem can be detected.