Physics: Year 1

Binding energy is the strong nuclear force by which the nucleus is held together. Also the amount of energy required to split an atom.

  • How close the electron is to the nucleus

  • How many protons are in the nucleus

Ionisation is the removal of an electron when it is struck with energy greater than its binding energy.

  1. Ionisation

  2. Electron drops to fill vacancy

  3. Releases energy in the form of electromagnetic radiation

IR(ME)R: ensures correct patient exposure, by mandating ID checks and the concept of ALARP

IRR17: protection of public and staff working with radiation to ensure radiation protection

  • designated control area with lead lined walls and doors, and warning signs

Electrons occupy a discrete energy state. Excitation is when electrons jump to higher energy levels when energy is transferred to them (electron drops back down to lower energy level releasing energy). Ionisation is when electrons are removed from orbitals when energy is transferred to them (creates free floating electron and ion).

Thermionic emission is the release of electrons due to heat.

  1. Characteristic radiation is when a high energy electron collides with an atom, removing an electron from its inner shell. Outer shell electron drops down to fill vacancy, releasing energy.

    • Photon energy is equal to the difference in energy levels between orbitals

    • Outer shell electron may be ejected instead of photon, called an auger electron

  1. Bremsstrahlung radiation occurs when an electrons interaction with a positive nucleus causes it to change direction, slow down and lose energy. This energy is emitted in the form of a photon.

    • Most x-rays are produced this way

    • Inherent filtering excludes low energy radiation which don’t contribute too imaging and only contribute to low patient dose

Beam hardening is when low energy radiation is attenuated, causing a greater change in low energy photon spectrum when the X-rays pass through material. This reduces the overall intensity of the spectrum and increases the average energy of the beam.

  • Quantity change means the number of photons change with the same distribution of energies

  • Quality changes means the number of photons and energy distribution changes

  • The focal spot narrows the range of electrons, forcing electrons to pass through a more precise spot and minimise unsharpness