Electromagnetics & Radiation Concept PDF

Electromagnetics& Radiation Concept Radiation Electromagnetics & Radiation Concept Electromagnetic radiation (Often abbreviated E-M radiation or EMR) is a form of energy exhibiting wave-like behavior as it travels through space. EMR has both electric and magnetic field components, which oscillate in...

Electromagnetics& Radiation Concept Radiation Electromagnetics & Radiation Concept Electromagnetic radiation (Often abbreviated E-M radiation or EMR) is a form of energy exhibiting wave-like behavior as it travels through space. EMR has both electric and magnetic field components, which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation. Electromagnetic radiation is classified according to the frequency of its wave. In order of increasing frequency and decreasing wavelength ,these are radio waves ,microwaves ,infrared radiation ,visible light ,ultraviolet radiation ,X-rays and Gamma rays. Electromagnetics & Radiation Concept Fig show: The electromagnetic spectrum Electromagnetics & Radiation Concept Radioactivity: what is it? All substance is made of atoms. These have electrons (e) around the outside, and a nucleus in the middle. The nucleus consists of protons (p) and neutrons (n), and is extremely small. Atoms are almost entirely made of empty space!. In some types of atom, the nucleus is unstable, And will decay into a more stable atom. This radioactive decay is completely spontaneous. Note: It's not the same as what happens in a nuclear power station (where neutrons whiz around and hit uranium nuclei, causing them to split). Electromagnetics & Radiation Concept Radioactivity: what is it? When an unstable nucleus decays, there are three ways that it can do so. It may give out: 1. Alpha particle α 2. Beta particle β 3. Gamma ray γ Electromagnetics & Radiation Concept Radioactivity: what is it? Alpha particles: Alpha particles are made of 2 protons and 2 neutrons. This means that when a nucleus emits an alpha particle, it loses 2 protons and so its atomic number decreases by 2 so they have a charge of +2. And Also, when a nucleus emits an alpha particle, its atomic mass decreases by 4 (that's 2 protons plus 2 neutrons) a mass of 4, The mass is measured in "atomic mass units", where each proton & neutron=1) Electromagnetics & Radiation Concept Radioactivity: what is it? Alpha particles: Alpha-decay occurs in very heavy elements, for example, Uranium and Radium. These heavy elements have too many protons to be stable. They can become more stable by emitting an alpha particle. Electromagnetics & Radiation Concept Radioactivity: what is it? Alpha particles: Example: Americium-241: α -source used in smoke detectors, which has an atomic number of 95 and an atomic mass of 241, will decay to Neptunium-237 which has an atomic number of 93 and an atomic mass of 237. Electromagnetics & Radiation Concept Radioactivity: what is it? Alpha particles: The equation would look like this: Electromagnetics & Radiation Concept Radioactivity: what is it? Alpha particles: Properties: Alpha particles are relatively slow and heavy Alpha particles have a low penetrating power - you can stop them with just a sheet of paper. Alpha particles have a large charge, so they easily ionize other atoms that they pass. Ionizing atoms requires energy, so alpha particles lose energy rapidly as they travel. Thus they have a range of only a few centimeters in air. Electromagnetics & Radiation Concept Radioactivity: what is it? Beta particles: Beta particles have a charge of minus 1, and a mass of about 1/2000th of a proton. This means that beta particles are the same as an electron. If a nucleus contains protons and neutrons, what's an electron doing coming out of a nucleus? ,To answer this, we know more about protons and neutrons: Protons & neutrons are made of combinations of even smaller particles, called "quarks". Under certain conditions, a neutron can decay, to produce a proton plus an electron. Electromagnetics & Radiation Concept Radioactivity: what is it? Beta particles: The proton stays in the nucleus, whilst the electron flies off at high speed This means that when a nucleus emits a β -particle: 1. the atomic mass is unchanged 2. the atomic number increases by 1 We can write them as ¯ or, e¯ because they're the same as an electron, Beta decay occurs in very "neutron-rich" elements, for example, Strontium-90 and Iodine-130. These elements have too few protons and too many neutrons to be stable, they can thus become more stable by emitting a beta particle. Electromagnetics & Radiation Concept Radioactivity: what is it? Beta particles: Example: Strontium-90 undergoes β decay and forms Yttrium-90 Electromagnetics & Radiation Concept Radioactivity: what is it? Beta particles: Properties: Beta particles are fast, and light. Beta particles have a medium penetrating power - they are stopped by a sheet of aluminum or plastics such as Perspex. Beta particles have a charge of -1, and weigh only a tiny fraction of a neutron or proton. As a result, β particles interact less readily with other atoms than alpha particles. Thus beta particles cause less ionization than alphas, and have a longer range, typically a few meters in air. Electromagnetics & Radiation Concept Radioactivity: what is it? Gamma rays: Gamma rays are waves, not particles. Gamma rays (γ ) are electromagnetic waves, rather like X rays and radio waves. This means that they have no mass and no charge. After a nucleus has emitted an α - particle or a β -particle, it may still have too much energy: we say it is in an "excited state". It can get rid of this energy by emitting a pulse of very high frequency electromagnetic radiation, called a gamma ray. So we sometimes write ⁰₀ Electromagnetics & Radiation Concept Radioactivity: what is it? Gamma rays: We don't find pure gamma sources - gamma rays are emitted alongside alpha or beta particles. Gamma emission isn't 'radioactive decay' because it doesn't change the state of the nucleus, it just carries away some energy Useful gamma sources include Technetium-99, which is used as a "tracer" in medicine. This is a combined beta and gamma source, and is chosen because betas are less harmful to the patient than alphas (less ionization) and because Technetium has a short half-life (just over 6 hours), so it decays away quickly and reduces the dose to the patient. Electromagnetics & Radiation Concept Radioactivity: what is it? Gamma rays: Properties: Gamma rays have a high penetrating power - it takes a thick sheet of metal such as lead, or concrete to reduce them significantly. Gamma rays do not directly ionize other atoms, although they may cause atoms to emit other particles which will then cause ionization. We don't find pure gamma sources - gamma rays are emitted alongside alpha or beta particles. Strictly speaking, gamma emission isn't 'radioactive decay' because it doesn't change the state of the nucleus, it just carries away some energy. Electromagnetics & Radiation Concept X ray: X rays have the same characteristics as gamma rays, although they are produced differently. When high-speed electrons hit metals, electrons are stopped and release energy in the form of an electromagnetic wave. This was first observed by Wilhelm Roentgen in 1895, who considered it a mysterious ray, and thus called it an X ray. X rays consist of a mixture of different wavelengths, whereas gamma-ray energy has a fixed value (or two) characteristic to the radioactive material. Electromagnetics & Radiation Concept Neutrons: Neutron particles are released following nuclear fission (splitting of an atomic nucleus producing large amounts of energy) of uranium or plutonium. In fact, it is neutrons that trigger the nuclear chain reaction to explode an atomic bomb. The human body contains a large amount of hydrogen (a constituent of water molecules that occupy 70% of the human body), and when neutrons hit the nucleus of hydrogen, i.e., a proton that is positively charged, the proton causes ionizations in the body, leading to various types of damage. At equivalent absorbed doses, neutrons can cause more severe damage to the body than gamma rays. Neutrons hardly damage cells because they do not carry any electrical charge Electromagnetics & Radiation Concept Health effects of gamma rays: All ionizing radiation causes similar damage at a cellular level, but because rays of alpha particles and beta particles are relatively non-penetrating, external exposure to them causes only localized damage, e.g. radiation burns to the skin. Gamma rays and neutrons are more penetrating, causing diffuse damage throughout the body (e.g.radiation sickness ,increased incidence of cancer) rather than burns. External radiation exposure should also be distinguished from internal exposure, due to ingested or inhaled radioactive substances, which, depending on the substance's chemical nature ,can produce both diffuse and localized internal damage. The most biological damaging forms of gamma radiation occur in the gamma ray window ,between 3 and 10 MeV, with higher energy gamma rays being less harmful because the body is relatively transparent to them. Electromagnetics & Radiation Concept Uses of gamma rays: Gamma-rays have the smallest wavelengths and the most energy of any wave in the electromagnetic spectrum. These waves are generated by radioactive atoms and in nuclear explosions. Gamma-rays can kill living cells, a fact which medicine uses to its advantage, using gamma-rays to kill cancerous cells. This property means that gamma radiation is often used to kill living organisms, in a process called irradiation. Applications of this include sterilizing medical equipment (as an alternative to autoclaves or chemical means), removing decay-causing bacteria from many foods or preventing fruit and vegetables from sprouting to maintain freshness and flavor. Electromagnetics & Radiation Concept Uses of gamma rays: Gamma-rays travel to us across vast distances of the universe, only to be absorbed by the Earth's atmosphere. Different wavelengths of light penetrate the Earth's atmosphere to different depths. Instruments aboard high-altitude balloons and satellites like the Compton Observatory provide our only view of the gamma-ray sky. Due to their tissue penetrating property ,gamma rays/X-rays have a wide variety of medical uses such as in CT Scans and radiation therapy. However, as a form of ionizing radiation they have the ability to effect molecular changes, giving them the potential to cause cancer when DNA is affected. The molecular changes can also be used to alter the properties of semi-precious stones , and is often used to change white topaz into blue topaz. Despite their cancer-causing properties ,gamma rays are also used to treat some types of cancer. Electromagnetics & Radiation Concept Uses of gamma rays: In the procedure called gamma-knife surgery, multiple concentrated beams of gamma rays are directed on the growth in order to kill the cancerous cells. The beams are aimed from different angles to concentrate the radiation on the growth while minimizing damage to the surrounding tissues. As an illustration of the radiation origin-process contributing to its name, a similar technique which uses photons rather than cobalt gamma decay, is called" Cyber knife. Electromagnetics & Radiation Concept Summary: Alpha particles are easy to stop, gamma rays are hard to stop Particles that ionize other atoms strongly have a low penetrating power, because they lose energy each time they ionize an atom. Radioactive decay is not affected by external conditions. Electromagnetics & Radiation Concept You need to know the information in this table: Type of radiation Alpha particle Beta particle Gamma ray  Or ⁴₂ Or He⁴₂  Or ¯  Mass (atomic mass units) 4 1/2000 0 Charge +2 -1 0 Speed Slow Fast very fast (speed of light) Ionizing ability High Medium 0 Penetrating power low Medium High Paper Aluminum Lead Symbol Stopped by Radioactive isotopes Electromagnetics & Radiation Concept Radioactive isotopes: You can think of different isotopes of an atom being different "versions" of that atom. Consider a carbon atom: It has 6 protons and 6 neutrons - we call it "carbon-12" because it has an atomic mass of 12 (6 plus 6). If we add a neutron, it's still a carbon atom, but it's a different isotope of carbon. One useful isotope of carbon is "carbon-14", which has 6 protons and 8 neutrons. Isotopes of an atom have the same number of protons, but a different number of neutrons Electromagnetics & Radiation Concept Terms and definitions Atomic number: The number of protons in the nucleus of the atom. Since the protons are positively charged. Atomic mass : The sum of the weights of both the neutrons and the protons in the atom. Nucleus : The densely packed kernel of the atom containing protons and neutrons. The diameter of the nucleus is 100,000 to 200,000 smaller than the whole atom Proton : An electrically positive particle found in the nucleus of the atom. Each proton is balanced by the charge of an electron surrounding the nucleus. The electrically neutral atom has the same number of negative electrons as positive protons. Electromagnetics & Radiation Concept Terms and definitions Neutron : An electrically neutral particle found in the nucleus with a mass almost that of the proton. In the fission process, neutrons are liberated. Electron : A small negatively charged particle that surrounds the nucleus to neutralize or charge balance the atom, with a mass about 1/1800 that of the proton. Beta particles are energetic electrons ejected from a radioactive nucleus. Element : The most basic physical substance composed of all the same type of atoms. Each atom will have the same number of protons. The number of neutrons can differ. Isotope : Atoms with the same number of protons, but differing in the number of neutrons present in the nucleus. Most elements have more than one isotope. Electromagnetics & Radiation Concept Terms and definitions Photon : The smallest unit of light. The photon is often described as a electromagnetic wave or wave packet. Light photons from red to blue in the visible spectrum have increasing energy. X-rays and gamma rays are energetic photons with thousands to millions of times the energy of light photons Electromagnetics & Radiation Concept Units of radiation measurement Roentgen (R): The roentgen is a unit used to measure a quantity called exposure. The roentgen measures the energy produced by gamma radiation in a cubic centimeter of air. This can only be used to describe an amount of gamma and X-rays, and only in air. The main advantage of this unit is that it is easy to measure directly, but it is limited because it is only for deposition in air, and only for gamma and x rays. Rad (Radiation Absorbed Dose): The rad is a unit used to measure a quantity called absorbed dose. This translates to the amount of energy actually absorbed in some material, and is used for any type of radiation and any material, but it does not describe the biological effects of the different radiations. Electromagnetics & Radiation Concept Units of radiation measurement Rem (Roentgen Equivalent Man): The rem is a unit used to derive a quantity called equivalent dose. This relates the absorbed dose in human tissue to the effective biological damage of the radiation. Not all radiation has the same biological effect, even for the same amount of absorbed dose, 1 rad of exposure results in 1 rem of dose. Curie (Ci): Is a unit used to measure a radioactivity. One curie is the number of particles per second from 1 gram of Radium, Often radioactivity is expressed in smaller units like: Tthousandths (mCi), Onemillionths (uCi) or even Billionths (nCi) of a curie. Electromagnetics & Radiation Concept Units of radiation measurement Gray (Gy): The gray is a unit used to measure a quantity called absorbed dose. This relates to the amount of energy actually absorbed in some material, and is used for any type of radiation and any material. One gray is equal to one joule of energy deposited in one kg of a material, but it does not't describe the biological effects of the different radiations. One gray is equivalent to 100 rads Sievert (Sv): Is a "quality factor" based on the type of particle. The sievert is a unit used to derive a quantity called equivalent dose. This relates the absorbed dose in human tissue to the effective biological damage of the radiation. Not all radiation has the same biological effect, even for the same amount of absorbed dose. One sievert is equivalent to 100 rem. Electromagnetics & Radiation Concept Dangers of radioactivity: The main danger from radioactivity is the damage it does to the cells in your body. Most of this damage is due to ionization when the radiation passes, although if levels of radiation are high there can be damage due to heating effects as your body absorbs the energy from the radiation, rather like heating food in a microwave oven. This is particularly true of gamma rays. Electromagnetics & Radiation Concept Radiation Is the flow of energy through space and matter. Some examples of radiation are visible light , radio waves ,and radiant heat. Radiation can be in the form of particles or waves Ionizing radiation is radiation that produces ions in matter. It is able to disrupt chemical bonds of molecules and cause biologically important changes. Electromagnetics & Radiation Concept Radiation When radiation enters the body and hits a cell, one of four things can happen: 1. Radiation may pass through the cell without doing damage 2. It may damage the cell, but the cell may be able to repair the damage before producing new cells 3. It may damage the cell in such a way that the damage is passed on when new cells are formed 4. It may kill the cell Electromagnetics & Radiation Concept Internal and External Exposure to Radiation: Radiation exposure may be internal or external. Internal exposure comes from eating or drinking contaminated food or water, or from breathing contaminated air. A radioactive substance can also enter the body through cuts in the skin. Alpha and beta radiation contribute to internal exposure. External exposure can come from beta, gamma and X-ray radiation that penetrates the body. Both internal and external radiation exposure can directly harm cells. Exposure to Hanford's radiation was primarily internal. Exposure from the atomic bombings in Japan was primarily external. Electromagnetics & Radiation Concept Effects of Radiation on the Human Body: Hair: The losing of hair quickly and in clumps occurs with radiation Exposure at 200 rems or higher. Brain: Since brain cells do not reproduce, they won't be damaged directly unless the exposure is 5,000 rems or greater. Like the heart, radiation kills nerve cells and small blood vessels, and can cause seizures and immediate death. Thyroid: The certain body parts are more specifically affected by exposure to different types of radiation sources. The thyroid gland is susceptible to radioactive iodine. In sufficient amounts, radioactive iodine can destroy all or part of the thyroid. By taking potassium iodide, one can reduce the effects of exposure. Electromagnetics & Radiation Concept Effects of Radiation on the Human Body: Blood System: When a person is exposed to around 100 rems, the blood's lymphocyte cell count will be reduced, leaving the victim more susceptible to infection. This is often referred to as mild radiation sickness. Early symptoms of radiation sickness mimic those of flu and may go unnoticed unless a blood count is done. According to data from Hiroshima and Nagasaki, show that symptoms may persist for up to 10 years and may also have an increased long-term risk for leukemia and lymphoma. Heart: Intense exposure to radioactive material at 1,000 to 5,000 rems would do immediate damage to small blood vessels and probably cause heart failure and death directly. Electromagnetics & Radiation Concept Effects of Radiation on the Human Body: Gastrointestinal Tract: Radiation damage to the intestinal tract lining will cause nausea, bloody vomiting and diarrhea. This is occurs when the victim's exposure is 200 rems or more. The radiation will begin to destroy the cells in the body that divide rapidly. These including blood, GI tract, reproductive and hair cells, and harm their DNA and RNA of surviving cells. Reproductive Tract: Because reproductive tract cells divide rapidly, these areas of the body can be damaged at rem levels as low as 200. Long-term, some radiation sickness victims will become sterile. Electromagnetics & Radiation Concept Other effect Immune System: Studies have shown that radiation exposure can weaken the immune system. While there are no studies concerning Hanford and autoimmune diseases, some Hanford-area residents are concerned that their exposure to radioactive materials has triggered such diseases. They believe that there are a higher-than-usual number of autoimmune disease cases among those who were exposed. Genetic Effects and Birth Defects: Genetic effects of radiation exposure occur when radiation damage to a parent's DNA code is transmitted to a child. Genetic effects caused by radiation fall into two categories: 1. effects that appear in the children of an exposed parent 2. effects that appear in later generations. Birth defects can arise spontaneously or through harm to normal developmental processes by radiation or by other toxic exposures. Electromagnetics & Radiation Concept Other effect