Back To CourseGCSE Physics: Practice & Study Guide
28 chapters | 188 lessons
Patricia is an experienced registered nurse who has worked in various acute care areas as well as in legal nurse consulting. She also has a BSChE.
In the minds of many people, radiation is a huge mushroom cloud ballooning catastrophically over massive areas, causing people to disintegrate and creating huge dinosaur-like, mutant creatures that glow in the dark. But in reality, it is a very natural phenomenon that occurs quite routinely throughout the entire universe, and not just in man-made sci-fi horror movies.
The term radiation simply means the emission of energy as particles or waves. The most popular usage of the term generally refers to electromagnetic radiation, or EMR, which covers a spectrum that ranges from low frequency radio waves upward through high frequency gamma waves.
There are many different terms in use that define units for measuring radiation under various circumstances. They provide an endless source of confusion for students and professionals alike. But, not to worry...the only ones we'll talk about here are the rem and the sievert, because these are the most relevant for measuring the effects of radiation on living biological tissue.
The sievert, which is expressed in units of energy per unit of mass, or joules per kilogram, is the most popular modern unit for measuring radiation. It expresses the absorbed dose of radiation, corrected for how harmful that particular type of radiation is to human tissue. The rem (acronym for Roentgen equivalent man) is just a smaller portion of the sievert. One sievert is equal to one hundred rems.
Humans on planet earth are exposed to radiation from natural sources every day. It has been estimated that the average human receives about 3mSv (millisievert) per year from naturally occurring radioactive materials and cosmic radiation from outer space. The two main types of radiation are non-ionizing radiation and ionizing radiation.
Non-ionizing radiation is radiation that has a lower frequency (or longer wavelength) in the EMR spectrum. These frequencies range from that of power lines, radios, and cell phones, up to visible light. Non-ionizing radiation is not powerful enough to break the chemical bonds in molecules. In general, it is not harmful to human health as radiation per se, but could be harmful in terms of the transfer of heat energy. An example of an emitter of non-ionizing radiation is a microwave oven.
Ionizing radiation is of higher frequency on the EMR spectrum than non-ionizing radiation. These frequencies range from visible light to gamma rays and x-rays. Ionizing radiation is generally considered to be more hazardous to human health than non-ionizing radiation because it can remove electrons from atoms. This means that it can damage living tissue and DNA. There are four basic types of ionizing radiation: Alpha, beta, gamma and x-ray, and neutron particles. All of these types of radiation are caused by the activity of unstable atoms.
Alpha radiation comes from the decay of heavy atoms such as uranium and radon. This radiation is in the form of particles, which are produced when an atom ejects two protons and two neutrons from its nucleus in the form of one subatomic fragment.
Alpha radiation cannot penetrate the skin, but it can be inhaled, swallowed, or can enter through a cut. After entering the tissues, it can cause a great deal of damage, possibly even cancer.
Like alpha radiation, beta radiation is caused by particles. However, these particles are negatively charged, and are smaller than alpha particles. They are emitted by smaller unstable atoms such as hydrogen-3 (tritium) and Carbon-14.
Beta particles can penetrate human tissue more easily than alpha particles and, at high energy, can even penetrate the skin. However, they are less harmful than alpha particles to human tissue because the ionizations they produce are more widely spaced. Like alpha particles, they are most harmful when inhaled or swallowed.
Gamma rays and X- rays, unlike alpha and beta radiation, do not consist of particles, but are packets of pure energy known as photons. Gamma rays, which originate inside the atom's nucleus, are very high-energy waves that can penetrate the whole body. They can cause changes in tissue and DNA, and it takes a dense layer of lead or concrete to stop them. Cobalt-60 and radium-266 are examples of elements that emit gamma rays.
X-rays are less penetrating than gamma rays and are lower in energy. The risk of damage to living tissue from x-rays used in medical diagnostic testing is very limited. However, one CT (computed tomography) scan emits a much larger amount of radiation. One CT scan emits about as much radiation as 200 chest x-rays.
Neutron particles travel at high speeds and can cause the objects with which they interact to become radioactive. Neutron radiation occurs primarily in nuclear reactors and is emitted as a result of induced nuclear fission.
All radioactive material decays, or becomes less radioactive over time. The half-life of a radioactive material is, simply put, the amount of time it takes for the material to lose half of its radioactive activity. Some radioactive elements have a half-life lasting only a few days, while others have a half-life lasting for thousands of years. It would seem to make sense that elements with a longer half-life would be more hazardous to human health, but this is not the whole truth. Elements with a short half-life will produce a greater amount of radiation over a shorter time, while elements with a longer half-life will produce less radiation over a longer time. Either way, both types of radioactive elements are dangerous, and great care must be taken in the storage of spent radioactive waste from sources such as nuclear power plants and from waste-generating industries such as hospitals.
The three most important components of protection against radiation exposure are time, distance, and shielding.
The United States Nuclear Regulatory Commission (NRC) is responsible for regulating the storage and disposal of radioactive waste in the United States. Because many of these wastes have half-lives that last many years, the environment must be protected from the radiation that they emit. Waste from nuclear power plants is stored in ''spent fuel pools'' which are designed to keep the waste from leaking into the ground or groundwater. These pools are made of thick layers of concrete, with steel liners.
This ''spent fuel pool'' type of storage is designed to be a temporary safety measure. More permanent storage and disposal methods for nuclear waste are still being explored.
Radiation is the emission of energy as particles or waves from a source, such as an unstable atom. The term ''radiation'' most popularly refers to electromagnetic radiation, or EMR. The EMR scale ranges from low to high energy frequencies, from radio waves to gamma rays. Non-ionizing radiation is in the lower part of the EMR scale, while ionizing radiation, which is more harmful to human health, is in the higher-energy range of the EMR scale.
The four types of ionizing radiation are alpha, beta, gamma and x-ray, and neutron radiation. Alpha and beta radiation are particulate in nature, while gamma and x-ray are in the form of photons. Neutron radiation is generated by nuclear fission.
The three most important elements in protecting human life from the health hazards of radiation are time, distance, and shielding. The less time spent near an emitting source, and the greater the distance from that source, the smaller is the dose of radiation received by a human. Sheilding also prevents radiation from penetrating the body to cause damage to living tissue, and is usually in the form of lead, concrete, or water. In the United States, it is the responsibility of the NRC to safely store radioactive waste from nuclear power plants and other industries that produce nuclear waste. Radioactive waste is dangerous to the environment because of the half-life of decaying material.
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Back To CourseGCSE Physics: Practice & Study Guide
28 chapters | 188 lessons