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Energy: joule (J) (kilogram-metre2 per second2)
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we use an energy unit based on a single (positive) electron charge when experiencing a voltage of 1 V, and this is referred to as the electron volt (eV).
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Radiation Exposure: coulomb per kilogram (C/kg) (Previously roentgen (r))
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Absorbed Dose: Gray (Gy) (one joule per kilogram) (Previously rad, 1 Gy =100 rads)
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Radioactivity: rate of decay of a radioactive material, becquerel (Bq) (one decay per second)
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A0 is the initial activity (at time t = 0) and At is the activity after time t. λ is a constant that is specific to the radioactive material under consideration.
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Z is the atomic number (i.e. the number of protons, determines the element)
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N is the number of neutrons
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A is the mass number (Z + N)
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The intensity of a point source of radiation decreases as the distance from the source is increased. The amount of decrease is inversely proportional to the square of the distance.
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Quarks: points of matter that exist with other quarks as a pair or triplet.
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Bound together by gluons
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Collections of quarks are hadrons. A triplet of quarks is known as a baryon.
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A Meson is one quark, and one anti-quark. The most commonly encountered meson is the pion, formed by anti-matter, extremely unstable.
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Six quarks - up, down, top, bottom, strange and charm; there are also six anti-quarks.
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Leptons: point particles that can exist in isolation
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Much lower mass than a quark
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May carry a negative unit charge (-1) or have no charge (0).
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Six leptons. The three charged leptons are electrons, muons and tau. The three uncharged leptons are neutrinos.
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The special antimatter anti-lepton is the positron.
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All known matter in the universe is made up of: The up and down quark; The electron lepton; The three uncharged neutrinos and the three uncharged anti-neutrinos
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All interactions are made up of forces between these particles. Four forces: 1. The strong force or nuclear force, mediated by gluons; 2. The electromagnetic force, mediated by photons; 3.The weak force, mediated by the W-bosons and the Z-boson; 4. Gravity, for which the force carrier particle still eludes detection
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Smallest unit in the composition of matter
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Composed of a central nucleus surrounded by one or more orbiting electrons
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The nucleus consists of two types of hadrons: Protons positively charged (+1), Neutrons neutrally charged
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Nucleons: protons and neutrons
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The nucleus is held together by the residual strong force, which occurs between quarks of neighbouring nuclei.
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Nucleons are about 2000 times heavier than electrons
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Atoms combine to form molecules and chemical compounds
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The size of the atom (its diameter) is about 10-10 m, whereas the nucleus has a diameter of 10-14 m, a factor of 10,000 smaller.
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The atom is largely unoccupied space which has an enormous bearing on interactions of radiation with matter, including human tissue.
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Heisenberg's Uncertainty Principle: the exact momentum (energy) and the exact position can't be known simultaneously
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Observing something alters it
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We can consider the atomic entity as either a: 1. particle (the localised ‘billiard ball’ approach) with particle diameter (d) and mass (m) 2. wave (an extended and vibrating phenomenon) with energy (E), wavelength (λ), and frequency (f).
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E = mc2
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Energy here is in J and must be converted into MeV.
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One atomic mass unit is 1/12 of the mass of the carbon-12 atom.
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Elements exist with different numbers of neutrons than the neutral atom
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'Isotope’ does not necessarily imply a radioactive material.
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Bohr model: electrons rotate around the nucleus in discrete energy shells that are stationary and arranged in increasing order of energy.
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A maximum number of electrons allowable in each shell
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K shell can hold 2 electrons, the L shell 8 electrons, the M shell 18 electrons, etc.
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Orbital electrons don't actually exist in precise circular orbits, but rather in imprecisely defined regions of space around the nucleus
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The electron’s position is defined by probability, with decreasing probability for locations outside of the ‘most likely’ regions
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Electrons have different binding energies, depending on the electron shell
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In the most stable configurations, electrons occupy the innermost shells where they are most tightly bound to the nucleus.
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Excitation: an electron is raised from a lower energy shell to an upper energy shell (releasing energy)
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Ionisation: an electron is removed completely from an atom
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Binding energy of an electron is the energy required to remove it completely from a shell
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Binding energy is higher for orbitals nearer the nucleus (KB>LB>MB).
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Binding energy increases with the charge (equal to the atomic number Z) of the nucleus
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Removing an electron/going from an inner to an outer shell, requires energy input
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An electron moving from an outer to an inner shell results in energy emission
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Cheatography n. The art of mapping complex subjects into clear, instantly navigable reference guides.
