Unit 5: Nuclear Physics

May 11, 2024

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Nuclear Physics Overview

Introduction

  • Focus on nuclear physics, specifically the nucleus and atomic physics.
  • Main topics: radiation and radioactivity.
  • No significant changes to Unit 5 in the syllabus update.

Target Audience

  • Applicable to core and extended students, including year 9 pre-IG or A course students.
  • Alpha scattering experiment and minor details mainly covered.

Main Topics

  • Atoms: Building blocks of matter consisting of protons, neutrons, and electrons.

    • Protons (+1 charge), neutrons (neutral, but consist of positive and negative charges), and electrons (-1 charge).
    • Unified Atomic Mass Constant (U) approximated to 1.66 x 10^(-27) kg.

  • Isotopes: Atoms with the same number of protons but different number of neutrons.

    • Nucleon number or mass number represents total number of protons and neutrons.
    • Atomic number represents number of protons.
    • Example: Helium 4 and 2, indicating 4 nucleons and 2 protons.

  • Radioactive Decay: Process where an unstable nucleus emits radiation to become stable.

    • Three main forms of radiation: alpha, beta, and gamma.
    • Nuclear reactions include fission (breaking large nucleus) and fusion (joining small nuclei).

  • Radioactive Emissions Types:

    • Alpha particles: 2 protons + 2 neutrons.
    • Beta particles: Electron emitted from nucleus.
    • Gamma rays: Electromagnetic waves with no mass/charge.

  • Decay Equations:

    • Total mass and proton number must remain constant before and after decay.

  • Background Radiation Measurement:

    • Geiger Muller tube for measuring ionization rates due to radiation.
    • Sources include cosmic rays, ground rocks, and various everyday materials.

  • Half-Life:

    • Time taken for half of the unstable nuclei or emitted radiation to decrease by half.

  • Alpha Scattering Experiment (Ernest Rutherford):

    • Demonstrated atom structure, indicating nucleus with concentrated mass and positive charge.

  • Deflection in Electric and Magnetic Fields:

    • Application of Fleming's left hand rule for alpha and beta particles.

  • Applications and Safety Precautions:

    • Mentioned applications in smoke detectors, sterilizing medical equipment, irradiating food, and measuring materials thickness.
    • Safety includes using lead shielding, reducing exposure time, and maintaining distance from radiation sources.

Key Points

  • Radioactivity involves alpha, beta, and gamma emissions, each with specific properties and effects on matter.
  • The nature of isotopes and their role in radioactive decay.
  • Importance of understanding decay equations and the half-life concept.
  • Practical applications of radioactive principles and safety precautions necessary in handling radioactive materials.