BRAINCAKERadioactivity
Revision notes for Radioactivity in OCR Physics A (H556). 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-lifeWhe 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 DatingPotassium-40 in rocks undergoes electron capture and changes to argon-40 and a neutrino.
- Radioactive TracersA radioactive tracer can be used to trace the path of movement of a substance through soe system e.g. the movement of blood through blood vessel…
- 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 results 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.