IGCSE Physics key definitions nuclear physics

IGCSE Physics Key Definitions For 0625 AND 0972 

Nuclear Physics

igcse-physics-definitions-nuclear-physics

OBJECTIVES:

By the end of this section, you will be able to :

  • Define key terms for IGCSE Phyiscs for 0625 and 0972 (9-1)  for   nuclear physics
  • Understand how marks have been alloted in the examination questions  for defining various quantities for nuclear physics
  • Become extremely confident in defining various terms using the correct scientific vocabulary as per the syllabus requirements for nuclear physics

IGCSE Physics Definitions / Nuclear  Physics

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  • Alpha particles

    Helium nuclei (2 protons + 2 neutrons), charge +2e, mass ? 4u; strongly ionising, low penetration.

  • Protons

    Positively charged particles in the nucleus; relative charge +1, relative mass ? 1.

  • Neutrons

    Neutral particles in the nucleus; relative charge 0, relative mass ? 1.

  • Electrons

    Negatively charged particles around the nucleus; relative charge ?1, relative mass ? 1/1836.

  • Positive ions (cations)

    Atoms/molecules that have lost one or more electrons, giving a net positive charge.

  • Nuclear fission

    The splitting of a heavy nucleus into lighter nuclei plus neutrons, releasing energy.

  • Proton number (atomic number, Z)

    Number of protons in the nucleus; determines the element.

  • Nucleon number (mass number, A)

    Total number of protons + neutrons in the nucleus.

  • Relative charge

    Charge compared with the proton’s charge magnitude: p = +1, e = ?1, n = 0.

  • Relative mass

    Mass compared on a common scale (? proton mass): p ? 1, n ? 1, e ? 1/1836.

  • Isotope

    Atoms of the same element (same Z) with different numbers of neutrons (different A).

  • Background radiation

    Low-level ionising radiation always present from natural and man-made sources (e.g. cosmic rays, rocks, radon, medical).

  • Ionising nuclear radiations

    Radiations that can remove electrons from atoms/molecules (e.g. alpha, beta, gamma).

  • Alpha radiation

    Emission of alpha particles; strongly ionising, very low penetration (stopped by paper/skin).

  • Beta radiation

    Emission of beta particles (electrons or positrons); moderate ionisation; stopped by a few mm of aluminium.

  • Gamma radiation

    High-energy electromagnetic waves from the nucleus; weakly ionising but highly penetrating; reduced by thick lead/concrete.

  • Ionising effect of radiations

    The ability of radiation to create ions by knocking electrons out of atoms, leading to chemical/biological changes.

  • Penetrating power of radiations

    Comparative ability to pass through materials: ? low < ? medium < ? high.

  • Radioactive decay

    Spontaneous, random change of an unstable nucleus to a more stable one with emission of radiation.

  • Alpha decay

    Nucleus emits an alpha particle; mass number ?4, atomic number ?2.

  • Beta decay

    Typically ??: a neutron becomes a proton + electron + antineutrino; atomic number +1, mass number unchanged. (?? is the opposite change.)

  • Gamma decay

    Excited nucleus emits a gamma ray; proton and nucleon numbers unchanged.

  • Radioactive decay equations

    Balanced nuclear equations showing parent ? daughter + emitted particle(s), conserving nucleon number and proton number.

  • Half-life

    The time for the activity (or number of undecayed nuclei) in a sample to fall to half its initial value.

  • Mutations

    Changes in the DNA of a cell; ionising radiation can increase the mutation rate. Some mutations are harmful (e.g. cancer), some neutral or rarely beneficial.

 

 

 

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