Nuclear Physics Notes

Particles

  • Proton

    • Relative Mass: 1

    • Charge: +1

  • Neutron

    • Relative Mass: 1

    • Charge: 0

  • Electron

    • Relative Mass: 1/2000

    • Charge: -1

Atomic Structure

  • Mass number: The total number of protons and neutrons in an atom's nucleus (also known as nucleon number).

  • Atomic number: The number of protons in an atom's nucleus. Determines the element.

  • Representation: ^{12}_6C (Carbon-12 example, where 12 is the mass number and 6 is the atomic number).

  • Neutral Atoms: Atoms have no overall charge because the number of electrons equals the number of protons, balancing the charges.

  • Atom Radius: Approximately 1 \times 10^{-10} meters.

Isotopes

  • Definition: Atoms of the same element (same number of protons) with different numbers of neutrons. This means isotopes have the same atomic number but different mass numbers.

Radioactivity

  • Definition: The process where unstable atomic nuclei release energy and particles to become more stable.

  • Measurement: Measured in Becquerels (Bq) and Curies (Ci). These units quantify the number of decays per second.

  • Detection:

    • Geiger Counter: A device used to detect and measure ionizing radiation.

    • Geiger-Muller Tube: A component of the Geiger counter that detects radiation and is connected to an electronic counter.

    • Count Rate: The number of decays recorded each second.

  • Nature of Radioactive Decay: A random process.

  • Hazards:

    • Irritation: Can occur from external exposure.

    • Contamination: Can occur from internal exposure (inside the body).

Types of Radioactive Emission

  • Alpha ($\alpha$) Particles

    • Composition: 2 neutrons and 2 protons (Helium nucleus).

    • Charge: +2

    • Mass: 4

    • Range: 1-5 cm in air.

    • Penetration: Stopped by skin/paper.

    • Ionization: High (30,000-50,000 ions per cm of air).

    • Uses: Smoke alarms.

    • Decay Equation Example: {}^{211}{83}Bi \rightarrow {}^{207}{81}Tl + {}^4_2\alpha

  • Beta ($\beta$) Particles

    • Composition: Fast-moving electrons.

    • Charge: -1

    • Mass: ~0

    • Formation: Formed when a neutron splits into a proton and an electron in the nucleus.

    • Range: 1 meter in air, 2 cm in tissue.

    • Penetration: Stopped by 2-3mm of aluminum.

    • Ionization: 50-100 ions per mm of air.

    • Uses: Measuring thickness of objects.

    • Decay Equation Example: {}^{90}{38}Sr \rightarrow {}^{90}{39}Y + {}^{0}_{-1}\beta

  • Gamma ($\gamma$) Radiation

    • Nature: Electromagnetic radiation emitted from the nucleus.

    • Charge: 0

    • Mass: 0

    • Penetration: Requires thick lead shielding to significantly reduce intensity.

    • Range: Infinite range in air, 1000 meters in tissue, 3 cm in lead.

    • Ionization: Low (3-5 ions per mm of air).

    • Uses: Medical imaging.

    • Decay Equation Example: {}^{211}{83}Bi \rightarrow {}^{207}{81}Tl + \gamma + {}^0_0\nu

      • Note: The last term {}^0_0\nu usually represents a neutrino, but it's not fully clear from the original notes.

Half-Life

  • Definition: The time it takes for the number of radioactive nuclei in a sample to decrease by 50%.

  • Alternative Definition: The time it takes for the count rate from a radioactive source to decrease by 50%.

  • Example:

    • Initial Count Rate: 1600

    • After 30 days: 800

    • After 60 days: 400

    • After 90 days: 200

    • Half-life = 30 days


Term 1: Proton
Definition 1: Relative Mass: 1, Charge: +1
Term 2: Neutron
Definition 2: Relative Mass: 1, Charge: 0
Term 3: Electron
Definition 3: Relative Mass: 1/2000, Charge: -1
Term 4: Mass number
Definition 4: The total number of protons and neutrons in an atom's nucleus (also known as nucleon number).
Term 5: Atomic number
Definition 5: The number of protons in an atom's nucleus. Determines the element.
Term 6: Neutral Atoms
Definition 6: Atoms have no overall charge because the number of electrons equals the number of protons, balancing the charges.
Term 7: Atom Radius
Definition 7: Approximately 1
imes 10^{-10} meters.
Term 8: Isotopes
Definition 8: Atoms of the same element (same number of protons) with different numbers of neutrons. This means isotopes have the same atomic number but different mass numbers.
Term 9: Radioactivity
Definition 9: The process where unstable atomic nuclei release energy and particles to become more stable.
Term 10: Measurement of Radioactivity
Definition 10: Measured in Becquerels (Bq) and Curies (Ci). These units quantify the number of decays per second.
Term 11: Geiger Counter
Definition 11: A device used to detect and measure ionizing radiation.
Term 12: Geiger-Muller Tube
Definition 12: A component of the Geiger counter that detects radiation and is connected to an electronic counter.
Term 13: Count Rate
Definition 13: The number of decays recorded each second.
Term 14: Nature of Radioactive Decay
Definition 14: A random process.
Term 15: Alpha ($\alpha$) Particles
Definition 15: Composition: 2 neutrons and 2 protons (Helium nucleus); Charge: +2; Mass: 4; Range: 1-5 cm in air; Penetration: Stopped by skin/paper; Ionization: High.
Term 16: Beta ($\beta$) Particles
Definition 16: Composition: Fast-moving electrons; Charge: -1; Mass: ~0; Formation: Formed when a neutron splits into a proton and an electron in the nucleus; Range: 1 meter in air, 2 cm in tissue; Penetration: Stopped by 2-3mm of aluminum; Ionization: 50-100 ions per mm of air.
Term 17: Gamma ($\gamma$) Radiation
Definition 17: Nature: Electromagnetic radiation emitted from the nucleus; Charge: 0; Mass: 0; Penetration: Requires thick lead shielding to significantly reduce intensity; Range: Infinite range in air, 1000 meters in tissue, 3 cm in lead; Ionization: Low.
Term 18: Half-Life
Definition 18: The time it takes for the number of radioactive nuclei in a sample to decrease by 50%. Or, the time it takes for the count rate from