Lec 1 Radio Lecture Notes PDF

 Ionizing radiation is a type of energy released by atoms that travels in the form of electromagnetic waves (gamma or X-rays) or particles (neutrons, beta or alpha).  Atomic structure  The basic unit of matter is the atom. The basic atomic model, as described by Ernest Rutherford and N...

 Ionizing radiation is a type of energy released by atoms that travels in the form of electromagnetic waves (gamma or X-rays) or particles (neutrons, beta or alpha).  Atomic structure  The basic unit of matter is the atom. The basic atomic model, as described by Ernest Rutherford and Neils Bohr in 1911, consists of a positively charged core surrounded by negatively-charge shells.  The central core, called the nucleus, contains protons and neutrons.  The shells are formed by electrons which exist in structured orbits around the nucleus.  Protons  Protons (p+) are positively charged and located in the nucleus of the atom. The number of protons determines the element The number of protons in the nucleus of an element is called the atomic number (Z).  For example a hydrogen atom has one proton in the nucleus. Therefore, the atomic number of hydrogen is 1. A helium atom has two protons in the nucleus, which means the atomic number is 2. Uranium has ninety-two protons in the nucleus and, therefore, has an atomic number of 92.  Neutrons  Neutrons (n) are uncharged and located in the nucleus of the atom. Atoms of the same element have the same number of protons, but can have a different number of neutrons.  Atoms which have the same number of protons but different numbers of neutrons are called isotopes. Isotopes have the same chemical properties; however, the nuclear properties can be quite different.  Electrons  Electrons (e-) are negatively charged and travel in specific orbits or energy levels about the nucleus. Each electron has energy which enables it to resist the positive charge of the nucleus. An atom is electrically neutral if the total electron charge equals the total proton charge. Electrons are bound to the positively charged nucleus by electrostatic attraction. Types of ionizing radiation  1)Alpha radiation occurs when an atom undergoes radioactive decay, giving off a particle (called an alpha particle) consisting of two protons and two neutrons. only travel a few centimeters in air. Alpha particles are unable to penetrate the outer layer of dead skin cells, but are capable, if an alpha emitting substance is ingested in food or air, of causing serious cell damage  2) Beta radiation takes the form of either an electron or a positron being emitted from an atom. Due to the smaller mass, it is able to travel further in air, up to a few meters, and can be stopped by a thick piece of plastic, or even a stack of paper. It can penetrate skin a few centimeters.  3) Gamma radiation, unlike alpha or beta, does not consist of any particles, instead consisting of a photon of energy being emitted from an unstable nucleus. Having no mass or charge, gamma radiation can travel much farther through air than alpha or beta.  Gamma waves can be stopped by a thick or dense enough layer material, with high atomic number materials such as lead  4)X-rays are similar to gamma radiation, with the primary difference being that they originate from the electron cloud. This is generally caused by energy changes in an electron, such as moving from a higher energy level to a lower one, causing the excess energy to be released. X-Rays are longer-wavelength and (usually) lower energy than gamma radiation  5)Neutron radiation consists of a free neutron, usually emitted as a result of spontaneous or induced nuclear fission. Able to travel hundreds or even thousands of meters in air, they are however able to be effectively stopped if blocked by a hydrogen-rich material, such as concrete or water. Sources of Radiation  1(Natural Sources)  A)Cosmic radiation comes from the sun and outer space. It consists of positively charged particles, as well as gamma radiation. At higher elevations, the amount of atmospheric shielding decreases and thus the dose increases.  Terrestrial Radiation(‫)االرضية‬  There are natural sources of radiation in the ground (i.e., rocks, building materials and drinking water  supplies). Some of the contributors to terrestrial sources are the natural radioactive elements radium, uranium and thorium. Many areas have elevated levels of terrestrial radiation due to increased concentrations of uranium or thorium in the soil.  Internal  The food we eat and the water we drink contains trace amounts of natural radioactive materials. These naturally occurring radioactive materials deposit in our bodies and, as a result, cause an internal exposure to radiation. Some naturally occurring radioactive isotopes include sodium, carbon, potassium. Most of our internal exposure comes from potassium.   Radon  Radon comes from the radioactive decay of radium, which is naturally present in the soil. Because radon is a gas, it can travel through the soil and collect in basements or other areas of a home. Human-made Sources The difference between human-made sources of radiation and naturally occurring sources is the place from which the radiation originates.  Medical Radiation Sources  In addition to x-rays, radioactive sources are used in medicine for diagnosis and  therapy.  Atmospheric Testing of Nuclear Weapons  Another human-made source of radiation includes residual fallout from atmospheric nuclear weapons testing in the 1950’s and early 1960’s. Atmospheric testing is now banned by most nations.  Consumer Products  Examples include TVs, older luminous dial watches, and some smoke detectors,  airport luggage inspection systems and building materials.  Nuclear Facilities 