Ionising Radiation from the NucleusOxford AQA IGCSE Physics: Flashcards

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Define radioactive decay.

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Define radioactive decay.: The random process by which an unstable nucleus emits particles or radiation to become more stable.
What is an alpha particle?: Two protons and two neutrons — a helium nucleus.
What is a beta particle?: A high-speed electron emitted as a neutron turns into a proton.
What is a gamma ray?: Electromagnetic radiation emitted from the nucleus.
Name three sources of background radiation.: Radioactive substances in the environment, space (cosmic rays), and devices such as X-ray machines.
Which type of nuclear radiation is the most strongly ionising?: Alpha particles.
Which type of nuclear radiation is the most penetrating?: Gamma rays.
What material stops most alpha radiation?: Paper or a few centimetres of air/skin.
What material is needed to absorb most beta radiation?: A few millimetres of aluminium.
What material is needed to significantly reduce gamma radiation?: Thick lead or concrete.
Define half-life.: The average time for the number of nuclei of an isotope in a sample to halve, or for the count rate to fall to half its initial level.
What is radioactive contamination?: The unwanted presence of radioactive atoms on or in a material.
What is irradiation?: Exposing an object to ionising radiation from a source; the irradiated object does not become radioactive.
Does an irradiated object become radioactive?: No — only contamination makes a material radioactive.