The primary difference between X-rays and gamma rays is that X-rays are emitted from processes outside the nucleus, but gamma rays originate inside the nucleus. Radioactive decay is a process by which unstable i. The rate of radioactive decay for each radioactive element is described by its half-life, or the amount of time it takes for around half of the radioactive atoms present to decay to a more stable form. Half-lives for different radioactive elements vary from fractions of seconds to billions of years.
Unstable radioactive atoms can go through a series of decays, or disintegrations, before reaching a stable form. Th has a half-life of 24 days and decays by beta particle emission to protactiniumm Pam , which has a half-life of only 1.
As shown in the aturally-occurring U decay series, the final product of the decay series is lead Pb , which is stable. Of note in this series is radon Rn , a radioactive gas that poses an inhalation hazard to workers and the public see the Hazard Recognition page. Source: U. Geological Survey. Uranium decay series naturally-occurring , which produces alpha, beta, and gamma radiation not shown.
Radioactivity is the number of energized particles or photons emitted by a source of radioactive material per unit of time. Another way to describe radioactivity is the number of decays also described as disintegrations occurring per unit of time. Units of measurement for radioactivity are the Curie Ci, traditional U.
What Happens to the Radiation Emitted? Ionizing radiation particles e. As shown in the graphic and table below, while alpha and beta particles are not very penetrating through other materials, gamma and X-rays are quite penetrating, as are neutrons. The illustration shows the penetrating power of different types of ionizing radiation, ranging from the least penetrating alpha particles to the most penetrating neutrons. When ionizing radiation interacts with humans, it is capable of damaging living cells in the human body.
Humans can be exposed: 1 to external radiation from a radiation source outside of the body, such as an X-ray from an X-ray machine; or 2 through internal exposure following inhalation breathing in , ingestion swallowing , or wound uptake i. In addition, the skin can become contaminated with radioactive materials when proper controls are not in place to prevent contamination or following an emergency.
More information about the health effects of ionizing radiation is provided on the Health Effects page. Units of measurement for radiation exposure are the Roentgen R, traditional U. The Hazard Recognition page provides information about external exposure and internal exposure. Absorbed dose is the amount of radiation energy absorbed per unit mass i.
Units of measurement for absorbed dose are the rad traditional U. Equivalent dose is the amount of radiation absorbed by an individual i. Units of measurement for equivalent dose are the rem traditional U.
Section Navigation. Facebook Twitter LinkedIn Syndicate. The Electromagnetic Spectrum: Ionizing Radiation. Minus Related Pages. On This Page. What is ionizing radiation? How much ionizing radiation am I exposed to?
What is the risk from exposure to ionizing radiation? More information. We are exposed to low levels of ionizing radiation every day. Ionizing radiation can fall into two categories: natural and manmade Ionizing Radiation from Natural Sources Ionizing radiation that comes from natural sources is typically at low levels. For more information on possible health effects from radiation and radiation dose, click here These low levels of exposure vary with location, altitude and type of building materials used in home construction.
In nature, sources of ionizing radiation include: Radiation from space cosmic and solar radiation Radiation from the earth terrestrial radiation Radon Radiation from building materials Ionizing Radiation from Manmade Sources Every day, we use Ionizing radiation to help us live healthy lives.
Natural Sources Natural sources of ionizing radiation usually release ionizing radiation at low levels, which also means the amounts of radiation absorbed by our bodies doses is usually small. For more information on radon, click here Manmade Sources Medical diagnostic exams are the main manmade source of ionizing radiation exposure in the U.
To receive email updates about this page, enter your email address: Email Address. What's this. Eyes High doses can cause cataracts. Thyroid Radioactive iodine can build up and cause cancer, particularly during growth. Lungs Breathing in radioisotopes can damage DNA. Stomach Radioactive isotopes can sit in the stomach and irradiate for a long time. Reproductive organs High doses can cause sterility or mutations. Skin Radiation can burn skin or cause cancer. While scientists think of these emissions in highly mathematical terms, they can be visualized either as subatomic particles or as rays.
Radiation's effects on humans can best be understood by first examining the effect of radiation on atoms , the basic building blocks of matter.
What is ionization? Atoms consist of comparatively large particles protons and neutrons sitting in a central nucleus, orbited by smaller particles electrons : a miniature solar system. Normally, the number of protons in the center of the atom equals the number of electrons in orbit. An ion is any atom or molecule that does not have the normal number of electrons. Ionizing radiation is any form of radiation that has enough energy to knock electrons out of atoms or molecules, creating ions.
How is ionizing radiation measured? Measurement lies at the heart of modern science, but a number by itself conveys no information.
Useful measurement requires both an instrument for measurement such as a stick to mark off length and an agreement on the units to be used such as inches, meters, or miles. The units chosen will vary with the purpose of the measurement.
For example, a cook will measure butter in terms of tablespoons to ensure the meal tastes good, while a nutritionist may be more concerned with measuring calories, to determine the effect on the diner's health. The variety of units used to measure radiation and radioactivity at times confuses even scientists, if they do not use them every day.
It may be helpful to keep in mind the purpose of various units. There are two basic reasons to measure radiation: the study of physics and the study of the biological effects of radiation. What creates the complexity is that our instruments measure physical effects, while what is of interest to some are biological effects.
0コメント