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Types and Sources of Ionizing Radiation
- Ionizing radiation consists of subatomic particles or electromagnetic waves.
- Gamma rays, X-rays, and higher energy ultraviolet rays are ionizing radiation.
- Lower energy ultraviolet, visible light, infrared, microwaves, and radio waves are non-ionizing radiation.
- Typical ionizing subatomic particles include alpha particles, beta particles, and neutrons.
- Secondary cosmic particles produced after cosmic rays interact with Earth's atmosphere include muons, mesons, and positrons.
- Cosmic rays and decay of radioactive isotopes are primary sources of natural ionizing radiation.
- Artificial sources include X-ray tubes, particle accelerators, and nuclear fission.
- Radioisotopes produced by cosmic rays on Earth contribute to background radiation.
- Ionizing radiation is used in fields like medicine, nuclear power, research, and industrial manufacturing.
- Proper measures must be taken to prevent excessive exposure to ionizing radiation.
Detection and Measurement of Ionizing Radiation
- Ionizing radiation is not immediately detectable by human senses.
- Instruments like Geiger counters are used to detect and measure ionizing radiation.
- High energy particles can produce visible effects on organic and inorganic matter.
- Ionizing radiation can cause acute radiation syndrome in humans.
- Visible effects of ionizing radiation include water lighting in Cherenkov radiation.
Directly Ionizing Radiation
- Charged particles with sufficient kinetic energy can ionize atoms directly.
- Examples of directly ionizing radiation include alpha particles, electrons, muons, and protons.
- Relativistic speeds of particles determine their ionizing capability.
- Alpha particles and energetic electrons were among the first types of directly ionizing radiation discovered.
- Natural cosmic rays primarily consist of relativistic protons and heavier atomic nuclei.
- Alpha particles are helium nuclei consisting of two protons and two neutrons.
- They are produced in the process of alpha decay.
- Alpha particles have low penetration power and can be absorbed by air or human skin.
- Ternary fission produces more energetic alpha particles that penetrate farther in air.
- Alpha particles are strongly ionizing and pose shielding problems in space.
Indirectly Ionizing Radiation
- Indirectly ionizing radiation is electrically neutral and does not strongly interact with matter.
- The bulk of ionization effects from indirectly ionizing radiation are due to secondary ionization.
- Photons can ionize atoms indirectly through the photoelectric effect and the Compton effect.
- The ejection of an electron from an atom at relativistic speeds turns it into a secondary beta particle that can ionize other atoms.
- Radiated photons are called gamma rays if produced by a nuclear reaction or radioactive decay within the nucleus, and x-rays if produced outside the nucleus.
- Photons are electrically neutral but can ionize atoms indirectly through the photoelectric effect and the Compton effect.
- Gamma rays are produced by nuclear reactions, subatomic particle decay, or radioactive decay within the nucleus.
- X-rays are produced outside the nucleus and typically have lower energy than gamma rays.
- The boundary between X-rays and gamma rays has historically been defined by energy thresholds, but there is overlap between the two.
- In astronomy, gamma rays and X-rays are functionally identical, differing only in the origin of the radiation.
Effects of Ionizing Radiation
- Ionizing radiation can cause nuclear transmutation and induced radioactivity.
- Neutron activation, alpha absorption, and photodisintegration are the mechanisms behind nuclear effects.
- Transmutations can change macroscopic properties and cause targets to become radioactive.
- Ionization of molecules can lead to radiolysis and formation of highly reactive free radicals.
- Ionizing radiation can accelerate chemical reactions such as polymerization and corrosion.
- Ionizing radiation can cause radiolysis, breaking chemical bonds.
- Highly reactive free radicals formed by ionization can react with neighboring materials.
- Ionizing radiation can accelerate existing chemical reactions.
- Optical materials can deteriorate under the effect of ionizing radiation.
- High-intensity ionizing radiation in air can produce a visible ionised air glow.
- Ionization of materials temporarily increases their conductivity.
- Damaging current levels can be permitted, posing a hazard in semiconductor microelectronics.
- Devices intended for high radiation environments may be made radiation hard.
- Proton radiation in space can cause single-event upsets in digital circuits.
- Gas-filled radiation detectors exploit the electrical effects of ionizing radiation.
- Adverse health effects of exposure to ionizing radiation can be grouped into deterministic and stochastic effects.
- Deterministic effects are harmful tissue reactions due to high doses from radiation burns.
- Stochastic effects include cancer development and heritable effects.
- The most common impact is the stochastic induction of cancer with a latent period of years or decades.
- The Linear no-threshold model (LNT) is the most widely accepted model for predicting the level of risk.
- Radiation and dose quantities can be measured using SI and non-SI units.
- Background radiation levels vary across different areas, ranging from as low as 1.5mSv/a to over 100mSv/a.
- The highest recorded natural radiation level on Earth's surface is 90µGy/h (0.8Gy/a) on a Brazilian black beach.
- Ramsar, an inhabited area, has the highest background radiation due to naturally radioactive limestone used in buildings.
- Some residents in Ramsar receive an average radiation dose of 10mGy per year, ten times more than the recommended limit.
- Despite the high levels, there is no compelling evidence of increased health risks for the residents.
- Cosmic radiation consists of relativistic particles from outside our solar system.
- It includes positively charged nuclei (ions) ranging from 1 amu protons to 26 amu iron nuclei.
- The energy of cosmic radiation can exceed what humans can create in particle accelerators.
- The dose from cosmic radiation is largely from muons, neutrons, and electrons.
- Airline flight crew workers receive more cosmic ray dose on average than any other worker.
- Most materials
Ionizing radiation (or ionising radiation), including nuclear radiation, consists of subatomic particles or electromagnetic waves that have sufficient energy to ionize atoms or molecules by detaching electrons from them. Some particles can travel up to 99% of the speed of light, and the electromagnetic waves are on the high-energy portion of the electromagnetic spectrum.
Gamma rays, X-rays, and the higher energy ultraviolet part of the electromagnetic spectrum are ionizing radiation, whereas the lower energy ultraviolet, visible light, nearly all types of laser light, infrared, microwaves, and radio waves are non-ionizing radiation. The boundary between ionizing and non-ionizing radiation in the ultraviolet area cannot be sharply defined, as different molecules and atoms ionize at different energies. The energy of ionizing radiation starts between 10 electronvolts (eV) and 33 eV.
Typical ionizing subatomic particles include alpha particles, beta particles, and neutrons. These are typically created by radioactive decay, and almost all are energetic enough to ionize. There are also secondary cosmic particles produced after cosmic rays interact with Earth's atmosphere, including muons, mesons, and positrons. Cosmic rays may also produce radioisotopes on Earth (for example, carbon-14), which in turn decay and emit ionizing radiation. Cosmic rays and the decay of radioactive isotopes are the primary sources of natural ionizing radiation on Earth, contributing to background radiation. Ionizing radiation is also generated artificially by X-ray tubes, particle accelerators, and nuclear fission.
Ionizing radiation is not immediately detectable by human senses, so instruments such as Geiger counters are used to detect and measure it. However, very high energy particles can produce visible effects on both organic and inorganic matter (e.g. water lighting in Cherenkov radiation) or humans (e.g. acute radiation syndrome).
Ionizing radiation is used in a wide variety of fields such as medicine, nuclear power, research, and industrial manufacturing, but presents a health hazard if proper measures against excessive exposure are not taken. Exposure to ionizing radiation causes cell damage to living tissue and organ damage. In high acute doses, it will result in radiation burns and radiation sickness, and lower level doses over a protracted time can cause cancer. The International Commission on Radiological Protection (ICRP) issues guidance on ionizing radiation protection, and the effects of dose uptake on human health.
ionizing radiation (countable and uncountable, plural ionizing radiations)
