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.
How is radiation used in radiotherapy?
Radiation (gamma) is used to destroy unwanted cells, generally for cancer.
How is radiation used in carbon dating?
The radiation from an object is measured, the half life of the carbon is then used to see how old the object is. It is used by archaeologists.
How is radiation used in smoke detectors?
Isotopes which emit alpha radiation are used in smoke detectors. The alpha radiation is picked up by the detector. If smoke is present, the alpha radiation is stopped by the smoke particles. No radiation reaches the detector and the alarm sounds.
Describe the structure of an atom in terms of protons, neutrons and electrons.
Protons and neutrons are in the POSITIVE nucleus of an element. Electrons orbit on NEGATIVE shells.
What are the dangers of ionising radiations?
Radiation can caused mutation in living organisms, and can damage cells and tissues.
What are the problems arising in the disposal of radioactive waste?
The waste emits radiation which can be dangerous. If it is put into water, it can poison ecosystems, similarly with land. It is normally buried underground, with the thinking that when it is less harmful, it can be dug up and disposed of.
What is the effect on the atomic and mass numbers of a nucleus if an alpha particle has been emitted?
Atomic number - decreased by two
Mass number - decreased by four
What is the effect on the atomic and mass numbers of a nucleus if a beta particle has been emitted?
Atomic number - increases by one
Mass number - remains the same
What is the effect on the atomic and mass numbers of a nucleus if gamma rays have been emitted?
No effect, as only energy is released.
