BRAINCAKERadioactivity
Revision notes for Radioactivity in AQA Physics (7408). Read the start of any lesson here, then sign in free for the whole lesson, the R.E.C.I.P.E. recall steps and the quiz.
- Rutherford's α-Particle Scattering Experiment.In 1911, Ernest Rutherford carried out an experiment to probe the atom.
- Rutherford's InterpretationMost of the atom's mass is concentration in a small volume at the centre of the atom i.e. the nucleus.
- RadioactivityAlpha radiation emitted by radioactive substances causes strong ionisation of air particles making air conduct electricity.
- Radioactivity ObservationsThe ionising effect of radiation can be seen using an ionisation chamber and pico-ammeter.
- Geiger TubeA Geiger tube is a sealed metal tube that contains argon gas at low pressure.
- The nature of α, β and γ Radiation.Alpha particles consist of two neutrons and two protons (i.e. a helium nucleus) and are positively charged.
- Gamma radiationThe intensity of gamma radiation emitted from a point source follows an inverse square law at an increasing distance away from a point.
- Radioactive ChangeAlpha emission results in the loss of 2 neutrons and 2 protons.
- The Dangers of RadioactivityIonising radiation such as u.v., X-rays, gamma rays and alpha and beta particles, damages living cells by damaging membranes, damaging DNA, creating…
- Background RadiationIn certain locations, radon gas can seep up from the ground into buildings.
- Radioactive Decay and Half-lifeWhen a substance decays, the mass of the initial isotope decreases exponentially as it is replaced by the new element.
- ActivityThe activity of a radioactive isotope is the number of nuclei in the isotope that disintegrate per second.
- Radioactive DecayRadioactive decay is random and spontaneous.
- Decay ConstantThe decay constant λ is the probability of an individual nucleus decaying per second.
- Radiocarbon datingCosmic rays knock out neutrons in the atmosphere which then collide with nitrogen to form radioactive Carbon-14.
- Argon datingThe radioactive isotope of potassium in ancient rocks decays into argon gas which becomes trapped in the rocks.
- Radioactive TracersA radioactive tracer can be used to trace the path of movement of a substance through some system e.g. the movement of blood through blood vessels…
- Thickness Monitoring and Engine WearEngine Wear A metal ring is made radioactive by exposing it to neutrons in a nuclear reactor.
- Power SourcesRadioactive isotopes can be used as power sources for remote devices such as satellites.
- N-Z GraphIf a graph of neutron number against proton number is plotted for all known isotopes of the elements it shows a line curving upwards and deviating…
- Decay SeriesMany radioactive decays result in the formation of isotopes which are themselves radioactive and decay further.
- Energy LevelsIf the daughter nucleus is formed in an 'excited' state after alpha or beta emission, the nucleus moves to its ground state by emitting gamma…
- TechnetiumA technetium generator consists of molybdenum-99 exposed to neutron radiation to make some of the nuclei unstable.
- Electron DiffractionThe diameter of a nucleus is about 1fm (10-15m).
- Nuclear Radius and DensityIf the radius is plotted against their mass number for different nuclei it can be shown that the radius R depends on the mass number.