Lec 7 G Physics PDF

# Classification of Radiation ## Radiation Basics: * Radiation is a form of energy motion through space. It is emitted by one object and absorbed or scattered by another. * It can come from unstable atoms that undergo radioactive decay, or it can be produced by machines. * Radiation travels from i...

# Classification of Radiation ## Radiation Basics: * Radiation is a form of energy motion through space. It is emitted by one object and absorbed or scattered by another. * It can come from unstable atoms that undergo radioactive decay, or it can be produced by machines. * Radiation travels from its source in the form of energy waves or energized particles. * There are different forms of radiation and they have different properties and effects. ## Types of Radiation * There are two kinds of radiation: non-ionizing radiation and ionizing radiation ### 1. Non-ionizing Radiation * Has enough energy to move electrons in an atom around or cause them to vibrate, but not enough to remove electrons from atoms. * Examples of this kind of radiation are radio waves, visible light, and microwaves. ### 2. Ionizing Radiation * Has so much energy it can knock electrons out of atoms, a process known as ionization. * Ionizing radiation can affect the atoms in living things, so it poses a health risk by damaging tissue and DNA in genes. ## Radiation Types and Production * Ionizing radiation comes from x-ray machines, cosmic particles from outer space and radioactive elements. * Radioactive elements emit ionizing radiation as their atoms undergo radioactive decay. * Examples of radioactive elements include: Uranium, Radium, Radon, and Polonium. ## Radioactive Decay * Radioactive decay is the emission of energy in the form of ionizing radiation. * The ionizing radiation that is emitted can include alpha particles, beta particles and/or gamma rays. * Radioactive decay occurs in unstable atoms called radionuclides. ## Types of Ionizing Radiation ### Alpha Particles * This is the decay process where two protons and neutrons leave the nucleus together. * An alpha particle is the nucleus of the Helium atom, which consists of two protons and neutrons. * Therefore, it has a charge of +2 and a mass of approximately 4 amu. * They are emitted primarily from extremely heavy nuclei (atomic number > 82, mass number > 200) * Alpha particles are positively charged and made up of two protons and two neutrons from the atom's nucleus. * Alpha particles come from the decay of the heaviest radioactive elements, such as uranium, radium and polonium. * Even though alpha particles are very energetic, they are so heavy that they use up their energy over short distances and are unable to travel very far from the atom. * This type of radiation is dangerous to humans because of the alpha particle's large size, high energy and short range. * Alpha particles cannot escape body tissues, so they deposit very high radiation doses internally. ### Beta Particles * Beta particles are small, fast-moving particles with a negative electrical charge that are emitted from an atom's nucleus during radioactive decay. * They are emitted by certain unstable atoms such as hydrogen-3 (tritium), carbon-14, and strontium-90. * Beta-minus particles have the same mass and charge as orbital electrons. * They are medium-range particles (several hundred centimeters in air, a few millimeters in tissue). ### Gamma Rays * Gamma rays are similar to visible light, but they have much higher energy. * Gamma rays are often emitted alongside alpha or beta particles during radioactive decay. * Gamma decay involves the emission of energy from an unstable nucleus in the form of electromagnetic radiation. * The processes result in the de-excitation of a nucleus that is left in an excited energy state following alpha or beta decay. ### X-rays * X-rays are similar to gamma rays in that they are photons of pure energy. * Both X-rays and gamma rays have the same basic properties, but they come from different parts of the atom. * X-rays are emitted from processes outside the nucleus, but gamma rays originate inside the nucleus. * They are generally lower in energy and, therefore, less penetrating than gamma rays. * X-rays can be produced naturally or by using electricity. ## Summary of Ionizing Radiation * **Directly ionizing:** Charged particles (e- , e+, p+, a, ions, etc. ) * **Indirect ionizing:** Neutral particles (n0, γ, X) The diagram shows a chart with the heading "Radiation." Underneath are two boxes: "Non-ionizing radiation" and "Ionizing radiation," These box headings are separated by a line. "Non-ionizing radiation" has a box below it: "Directly ionizing". Under that box are the words "Charged particles", "e- , e+, p+, a, ions, etc." "Ionizing radiation" has a box below it called "Indirect ionizing." Beneath that box are the words: "Neutral particles", "n0, γ, X"