Types of Radiation & Their Interactions with Matter

The groundbreaking work of Becquerel, the Curies, and Rutherford studying radioactivity revealed a diverse range of radiation types and their interactions with matter. This field has captivated scientific and societal interest for over a century, with billions of dollars invested globally in research.

In simple terms, radiation describes the movement of energy through space, in either wave form (such as through electromagnetic radiation) or through high energy particles (such as electrons or heavy charged particles). The study and measurement of radiation encompasses fundamental investigations into how radiation interacts with matter in nuclear and particle physics, studies on the biological effects of radiation, and the development of applications in medical diagnostics (beyond early imaging), industrial materials testing, and pursuing clean energy through nuclear power.

Types Of Radiation

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The term "radiation" encompasses a diverse array of energy and matter forms interacting through fundamental forces of nature. We can categorize these based on their constituent particles, which will also affect how they are detected and measured:

• Electromagnetic Radiation

  Electromagnetic radiation includes gamma rays, x-rays, ultraviolet, visible, infrared, microwave, and radio waves. This electromagnetic radiation can interact with matter through several methods, such as via photon absorption or Compton scattering. By measuring how photons interact with matter, we can investigate a wide range of things from fundamental physical principles to very specific material investigation.

• Light Charged Particles

  This includes any particle with small mass and electric charge, such as electrons, positrons, muons, and other subatomic particles. High energy electrons and other light particle will interact with matter, losing energy energy through both collisional energy losses and radiative loss. Collisional energy losses can be measured through the transfer of kinetic energy to other particles. Radiative losses, through processes such as Bremsstrahlung, results in light emission. These particles are often involved in many reactions, so precise measurement is difficult. However, measurement of high energy electrons, also known as beta particles, is crucial for many spectroscopy techniques.

• Heavy Charged Particles

  This includes particles such as protons, alpha particles (helium nuclei), and other atomic nuclei with significant mass and charge. Heavy particles with a large atomic mass, are often unstable, so some particles are particularly prone to radiative emission or reactions. Another key processes included in heavy charged particle radiation is nuclear fission, where two new nuclei are produced from one heavy unstable nucleus. This process also releases a lot of energy, and is the underlying principle of nuclear energy generation.

• Neutron Radiation

  Radition can also take the form of free neutrons. Nuetrons are neutral particles typically residing within the nucleus of an atom. Free neutrons can penetrate deeply into a medium before interacting with any atoms, due to their neutral charge. This makes them useful to studying the deep structure of a material.

• Exotic Particles

  Particles found primarily in high-energy environments like particle accelerators and supernovae, such as neutrinos, mesons, and quarks.

How Can Radiation Be Detected or Measured?

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These diverse forms of radiation interact with matter in various ways, depending on their energy and the properties of the medium. Key interaction mechanisms include:

• Ionization: The removal of electrons from atoms or molecules.
• Excitation: The elevation of electrons or nucleons to higher energy states within an atom or nucleus.
• Scattering: The deflection of radiation particles by collisions with atoms or nuclei, which can be elastic (conserving kinetic energy) or inelastic (involving energy transfer).
• Nuclear Reactions: Processes like fission (splitting of a heavy nucleus) and fusion (combining of light nuclei), which involve significant changes to the atomic nucleus.

Many scientists dedicate their careers to exploring specific types of radiation and their interactions. Modern nuclear and particle physics research delves into the properties of exotic particles and their interactions. For instance, neutrino physicists investigate neutrino oscillations, a phenomenon where neutrinos "quantum shift" between different types, and how that depends on the medium in which they propagate. Even in these experiments, physicists are only able to learn about subatomic particles by how they fundamentally interact with matter inside a detector.

Further Resources

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