Physics of Radiation

Physics of Radiation

• Radiation is the emission of energy as electromagnetic waves or as moving subatomic particles, carrying energy.
• Types include:
  • Electromagnetic radiation (e.g., radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays): characterized by oscillating electric and magnetic fields. Frequency and wavelength are inversely proportional.
  • Particle radiation (e.g., alpha, beta, and neutron radiation): involves the emission of subatomic particles like alpha particles (helium nuclei), beta particles (electrons or positrons), and neutrons.
• Characteristics of radiation:
  • Energy: higher frequency, shorter wavelength radiation carries more energy.
  • Wavelengths: different types of radiation have different ranges of wavelengths.
  • Frequency: frequency directly related to energy.
• Interactions with matter:
  • Absorption: radiation's energy is transferred to the absorbing material.
  • Reflection: radiation bounces off a surface.
  • Transmission: radiation passes through a material.
  • Scattering: radiation's direction is altered by interaction with matter.

Structure of the Atom

• Atoms are the basic building blocks of matter. They consist of a nucleus containing protons and neutrons, surrounded by orbiting electrons.
• Nucleus:
  • Positively charged.
  • Contains most of the atom's mass.
  • Protons: positively charged particles
  • Neutrons: neutral particles
• Electron cloud:
  • Negatively charged electrons orbit the nucleus.
  • Occupy regions called orbitals or shells.
  • Relatively small mass compared to protons and neutrons.
• Atomic number: the number of protons in the nucleus. This uniquely identifies an element.
• Mass number: the sum of protons and neutrons in the nucleus.
• Isotopes: atoms of the same element with different numbers of neutrons. Their mass numbers are different, but atomic numbers are the same.
• Atomic models:
  • Early models (e.g., Thomson's plum pudding model) were inaccurate.
  • Bohr model introduced quantized energy levels for electrons orbiting the nucleus.
  • Modern quantum mechanical model describes electrons in terms of probability distributions (orbitals).
• Electron configurations: arrangement of electrons in different energy levels and sublevels within the atom. These configurations are essential for understanding chemical bonding and reactivity.
• Radioactive decay:
  • Some isotopes are unstable and undergo radioactive decay, emitting radiation to become more stable.
  • Types of decay: alpha, beta, and gamma.

Radiation and Atomic Structure Relationship

• Radioactive decay processes involve changes in the nucleus of an unstable atom. These changes lead to the emission of radiation, as the atom converts into a more stable state.
• The specific radioactive decay process and the resulting emitted radiation are related to the atomic structure of the unstable nucleus. For example, different unstable isotopes will emit different types of radiation as they decay to achieve stability.