Alpha, beta and gamma radiation - penetration, uses and dangers Lesson 2: Alpha, Beta and Gamma Introduction In this lesson we'll introduce the three most important kinds of nuclear radiation: alpha, beta and gamma. We’ll see how their different properties affect what they can be used for and in what ways they may be harmful. What is alpha, beta and gamma radiation? We're not going to go into details about the exact origins of alpha, beta and gamma radiation in this lesson. Animation giving an idea of the relative size and speed of alpha, beta and gamma radiation. For the moment we'll say that alpha and beta radiation consist of tiny particles, much smaller than an atom. They move incredibly fast, perhaps thousands of kilometres per second. Gamma radiation is a sort of invisible, very high-energy light. Alpha, beta and gamma are the first three letters of the Greek alphabet. The types of radiation are named in the order that they were discovered. Americium-241, an alpha source Americium (pronounced a-meh-rees-ee-um) is a metal. It's radioactive and gives off alpha radiation so we call it an alpha source. In school experiments we only use a tiny radioactive source the size of a grain of sand.

It's normally enclosed in a steel tube with a wire mesh covering one end. This means you can't touch the source directly and the radiation only escapes in one direction. There's often a prong so you can pick up the source with pliers. Animation showing how a radioactive source is often confined in a small protective chamber with an open end so you can experiment with a beam of radiation. Alpha radiation doesn't go far but is very damaging Alpha radiation gets stopped by a few centimetres of air or a thin sheet of paper. You may think that this means alpha radiation is quite weak but in fact the opposite is the case. Activity Finding the penetrating power of alpha radiation. Alpha radiation is like a big heavy ball rolled across a lawn. It doesn't go very far because it loses a lot of energy flattening out the bumps in the ground. In other words the heavy ball interacts strongly with the ground. Animation comparing an alpha particle to a big, heavy ball. This is what alpha radiation does to air. Each alpha particle loses its energy by ripping the air atoms to pieces as it flies past. Eventually it loses all its energy and just stops harmlessly.

The difference between irradiation and contamination The best way to stay safe is to keep away from an alpha emitter, like americium-241. You don't have to be very far, half a metre is fine. This is easy if the americium is a solid block but if it’s dissolved in a liquid or crushed into dust then you need to be much more careful. Dust can be blown long distances by the wind. If you inhaled some americium dust then your lung linings could be damaged as the alpha radiation tore up the molecules in your cells. When radioactive dust lands on something we say that thing has been ‘contaminated’. Contamination is about the stuff that’s emitting the radiation, like dust or water. Contamination can be a risk over long distances. Animation explaining the difference between contamination and irradiation. Irradiation is about the radiation itself like alpha, beta or gamma. Radiation can’t travel far so is not a risk over long distances. Alpha particles cause lots of ionization in a short distance Alpha radiation is up to twenty times more damaging than other kinds because it tears up atoms so much. This tearing up process is called ‘ionization’ and we’ll see what it means in more detail later.

The torn-up air particles (or “ions”) have an electric charge so they can be part of an electric circuit. Animation of alpha particles ionizing air molecules. Using americium-241 in a smoke detector One use of americium-241 is in smoke detectors. The alpha particles tear up the neutral air molecules. The resulting positive and negative ions can be part of an electric circuit. In normal use this circuit is complete. When there's a fire smoke particles enter the detector. The ions stick to the much bigger smoke particles because charged things are attracted to uncharged things. This breaks the circuit. A different circuit senses the break and sets off the alarm. Simulation of a smoke detector that uses an alpha source. Strontium-90, a beta source Strontium-90 is a soft, highly reactive metal. It gives off beta radiation. Beta particles can go through a few metres of air. They can pass through paper and thin aluminium easily but they get stopped by even a thin piece of lead. Activity Finding the penetrating power of beta radiation. Beta goes further than alpha but is less damaging A beta particle can get through a few metres of air. It's like a golf ball rolled fast along our grassy lawn.

The ball jumps and bounces over the ground. You can see it’s path through the grass but it doesn’t flatten everything like alpha. The ‘beta radiation ball’ breaks some of the blades of grass but most of them spring back unharmed. We say that beta radiation is not so strongly ‘ionizing’ as alpha because it doesn’t rip atoms to bits as much as it passes. Animation comparing the ionizing power of alpha and beta particles. Does this mean beta radiation is safer? Yes, it does. Beta is safer than alpha. Beta radiation will do less harm to a cell as it passes through. But it can reach more cells that it can harm a bit. Radiation is most harmful if a cell is badly damaged but not killed. Beta’s longer range in air means you have to be a few metres away from the radioactive source in order to be safe. So you can protect yourself from exposure to beta radiation by keeping your distance. You could also use a thin lead shield but sometimes this can produce X-rays , which carry their own risk. It's is much harder to keep your distance if the beta emitter is a dust or carried in water so it can spread throughout the environment.

Again, beta radiation is most dangerous if you breath in or swallow a substance that emits beta radiation. Remember it’s the radioactive substance that gets breathed in. You can’t breath in ‘radiation’. Using beta particles to measure thickness Imagine we want to manufacture some thin sheet aluminium. A good way of controlling the thickness is to shine beta radiation through the aluminium and measure how much gets through. The less beta radiation that gets through, the thicker the sheet is. Beta gauges are very sensitive but the real advantage is that you can measure the aluminium without having to touch it as it races past. Often the system is computer controlled so the rollers are moved automatically to keep the thickness the same. Simulation of how a beta source can be used to measure the thickness of aluminium foil. Tiny beta capsules can be used to treat cancer The capsules are injected around the cancer and the beta radiation kills the cancer cells. Radiation is particularly damaging to cells that are in the process of dividing. Cancer cells divide much more often than healthy cells. This means cancer cells tend to be killed while most of the healthy cells are unharmed. Animation showing how capsules containing a beta emitter can be used to treat cancer.

Gamma radiation is often emitted with alpha and beta Gamma radiation is a type of invisible, very high energy light. It's the same type of stuff as light, infrared, radiowaves and X-rays. These are all types of electromagnetic radiation. Graphic showing how gamma radiation fits into the electromagnetic spectrum. Gamma radiation isn't emitted by itself, only after another event like alpha or beta decay. Normally it's emitted at almost exactly the same time. Gamma rays can pass through lead but aren't very damaging Gamma rays can pass through a thin sheet of lead with very little effect. You need about 10 cm of lead to stop most gamma rays completely. Gamma rays are like a wind blowing over our lawn. It occasionally blows down a blade of grass but mostly it just passes through undisturbed. Activity Finding the penetrating power of gamma radiation. Gamma rays are weakly ‘ionizing’. They can rip an atom to pieces but they don’t do it very often. Gamma radiation spreads out All radiation spreads out as it gets further from the source. But alpha and beta radiation can be absorbed by the surroundings quite easily so this spreading is more difficult to see. Animation showing gamma radiation spreading out.

Gamma radiation on the other hand passes through most things without really noticing so the spreading out is much easier to detect. So gamma radiation tends to pass through your body without interfering with the molecules that make up your cells too much. But you need to be quite a long way away from a gamma source in order not to receive much radiation. One safety precaution is to keep gamma sources in lead containers. Wearing a lead apron also helps protect people whose job means they have to handle gamma sources regularly. Since lead can itself be toxic another metal like titanium can be used instead for clothing. Gamma rays are commonly used for tracers Gamma can easily pass through solid materials unlike alpha and beta. If we use a source that doesn’t give off very much gamma radiation then we can use it as a ‘tracer’ in the environment. For example, maybe we know an oil pipeline is probably leaking but we don’t know where. First of all a gamma emitter is mixed with the oil. The oil carries the emitter to the leak. The leaking oil mixes in with the earth around the pipe and ends up closer to the ground. The gamma radiation can pass through the ground and be picked up by the gamma detector so you can tell where the leak is.

Simulation of how a gamma tracer can be used to find a leak in an oil pipeline. Gamma radiation can sterilize medical equipment Intense gamma radiation can kill bacteria and other microbes. This makes it useful for sterilizing medical equipment. The gamma radiation can reach inside even the most complex shapes and it doesn't expose delicate equipment to high temperatures. There's also no need to rinse off chemicals afterwards. Animation showing the principle of how gamma radiation can be used to sterilize medical equipment. Gamma radiation can be used to see inside a patient In low concentrations gamma radiation is not very damaging to living cells because it tends to pass straight through them. Doctors can use gamma radiation to ‘see’ inside a patient. But instead of shining gamma radiation at a patient from the outside they inject a gamma emitter into the patient and look at the radiation that comes out. Animation of how a gamma tracer can be used to see inside a patient. Say the doctor wants to get an image of a tumour in the patient’s brain. X-rays are no good because X-rays only show bones and denser tissues. She selects a harmless chemical that will tend to accumulate in the brain tumour. Then she reacts the chemical with another chemical that emits gamma radiation. This is called radioactive ‘tagging’.

A common tag is called technetium-99m . The tagged chemical is injected into the patient’s vein. It spreads around the body but tends to build up in the brain tumour. So the brain tumour gives off gamma radiation. The doctor then uses a special camera called a ‘gamma camera', which is sensitive to the gamma radiation given off. The image is built up quite slowly because the gamma source used is not very ‘bright’ for improved safety. So it takes a while for the camera to capture enough packets of gamma radiation. The doctor may takes lots of images of the tumour from different angles. Sophisticated computer software can then build a 3-D image of the tumour. The computer can then display slices through the tumour. Displaying slices is called ‘tomography’. Gamma radiation can be used as a 'knife' Gamma radiation can also be used to treat some kinds of cancer. This is called ‘external radiotherapy’ because the radioactive source is not injected into the patient. This machine is called a ‘gamma knife’. The gamma rays can pass through hundreds of holes in a lead ring. It’s only in the middle of the ring that the gamma radiation is very concentrated.

The patient is moved round so that the gamma radiation kills the cancer cells. Animation of the idea of external gamma radiotherapy Basic Nuclear Science Information Nuclear Structure | Radioactivity | Alpha Decay | Beta Decay | Gamma Decay | Half-Life | Reactions | Fusion | Fission | Cosmic Rays | Antimatter Please note, when you click on the keywords below, you will get a pop-window. If the new window does not have a scroll bar, you can click on the pop-window and use your arrow keys or scroll wheel to view the rest of the contents of the glossary. Nuclear Structure . An atom consists of an extremely small, positively charged nucleus surrounded by a cloud of negatively charged electrons . Although typically the nucleus is less than one ten-thousandth the size of the atom, the nucleus contains more than 99.9% of the mass of the atom! Nuclei consist of positively charged protons and electrically neutral neutrons held together by the so-called strong or nuclear force. This force is much stronger than the familiar electrostatic force that binds the electrons to the nucleus, but its range is limited to distances on the order of a few x10-15 meters.

The number of protons in the nucleus, Z, is called the atomic number . This determines what chemical element the atom is. The number of neutrons in the nucleus is denoted by N. The atomic mass of the nucleus, A, is equal to Z + N. A given element can have many different isotopes, which differ from one another by the number of neutrons contained in the nuclei. In a neutral atom, the number of electrons orbiting the nucleus equals the number of protons in the nucleus. Since the electric charges of the proton and the electron are +1 and -1 respectively (in units of the proton charge), the net charge of the atom is zero. At present, there are 112 known elements which range from the lightest, hydrogen, to the recently discovered and yet to-be-named element 112. All of the elements heavier than uranium are man made. Among the elements are approximately 270 stable isotopes, and more than 2000 unstable isotopes. Radioactivity In 1896, Henri Becquerel was working with compounds containing the element uranium.

To his surprise, he found that photographic plates covered to keep out light became fogged, or partially exposed, when these uranium compounds were anywhere near the plates. This fogging suggested that some kind of ray had passed through the plate coverings. Several materials other than uranium were also found to emit these penetrating rays. Materials that emit this kind of radiation are said to be radioactive and to undergo radioactive decay . In 1899, Ernest Rutherford discovered that uranium compounds produce three different kinds of radiation. He separated the radiations according to their penetrating abilities and named them a alpha , b beta , and g gamma radiation, after the first three letters of the Greek alphabet. The a radiation can be stopped by a sheet of paper. Rutherford later showed that an alpha particle is the nucleus of a He atom, 4He. Beta particles were later identified as high speed electrons. Six millimeters of aluminum are needed to stop most b particles. Several millimeters of lead are needed to stop g rays , which proved to be high energy photons . Alpha particles and g rays are emitted with a specific energy that depends on the radioactive isotope.

Beta particles, however, are emitted with a continuous range of energies from zero up to the maximum allowed for by the particular isotope. α decay The emission of an a particle, or 4He nucleus, is a process called a decay. Since a particles contain protons and neutrons, they must come from the nucleus of an atom. The nucleus that results from a decay will have a mass and charge different from those of the original nucleus. A change in nuclear charge means that the element has been changed into a different element. Only through such radioactive decays or nuclear reactions can transmutation , the age-old dream of the alchemists, actually occur. The mass number, A, of an a particle is four, so the mass number, A, of the decaying nucleus is reduced by four. The atomic number, Z, of 4He is two, and therefore the atomic number of the nucleus, the number of protons, is reduced by two. This can be written as an equation analogous to a chemical reaction.

For example, for the decay of an isotope of the element seaborgium, 263Sg: 263Sg ----> 259Rf + 4He The atomic number of the nucleus changes from 106 to 104, giving rutherfordium an atomic mass of 263-4=259. a decay typically occurs in heavy nuclei where the electrostatic repulsion between the protons in the nucleus is large. Energy is released in the process of a decay. Careful measurements show that the sum of the masses of the daughter nucleus and the a particle is a bit less than the mass of the parent isotope. Einstein's famous equation, E=mc2, which says that mass is proportional to energy, explains this fact by saying that the mass that is lost in such decay is converted into the kinetic energy carried away by the decay products. β Decay Beta particles are negatively charged electrons emitted by the nucleus. Since the mass of an electron is a tiny fraction of an atomic mass unit, the mass of a nucleus that undergoes b decay is changed by only a tiny amount. The mass number is unchanged. The nucleus contains no electrons.

Rather, b decay occurs when a neutron is changed into a proton within the nucleus. An unseen neutrino, , accompanies each b decay. The number of protons, and thus the atomic number, is increased by one. For example, the isotope 14C is unstable and emits a β particle, becoming the stable isotope 14N: 14C ----> 14N + e- + In a stable nucleus, the neutron does not decay. A free neutron, or one bound in a nucleus that has an excess of neutrons, can decay by emitting a b particle. Sharing the energy with the b particle is a neutrino. The neutrino has little or no mass and is uncharged, but, like the photon, it carries momentum and energy. The source of the energy released in b decay is explained by the fact that the mass of the parent isotope is larger than the sum of the masses of the decay products. Mass is converted into energy just as Einstein predicted. γ Decay Gamma rays are a type of electromagnetic radiation that results from a redistribution of electric charge within a nucleus. A g ray is a high energy photon.

The only thing which distinguishes a g ray from the visible photons emitted by a light bulb is its wavelength; the g ray's wavelength is much shorter. For complex nuclei there are many different possible ways in which the neutrons and protons can be arranged within the nucleus. Gamma rays can be emitted when a nucleus undergoes a transition from one such configuration to another. For example, this can occur when the shape of the nucleus undergoes a change. Neither the mass number nor the atomic number is changed when a nucleus emits a g ray in the reaction 152Dy* ----> 152Dy + γ Half-life The time required for half of the atoms in any given quantity of a radioactive isotope to decay is the half-life of that isotope. Each particular isotope has its own half-life. For example, the half-life of 238U is 4.5 billion years. That is, in 4.5 billion years, half of the 238U on Earth will have decayed into other elements. In another 4.5 billion years, half of the remaining 238U will have decayed. One fourth of the original material will remain on Earth after 9 billion years.

The half-life of 14C is 5730 years, thus it is useful for dating archaeological material. Nuclear half-lives range from tiny fractions of a second to many, many times the age of the universe. For more information on half-life and isotopes, please refer to the Isotopes Project at LBNL where you can also find the Table of Isotopes online. Reactions If nuclei come close enough together, they can interact with one another through the strong nuclear force, and reactions between the nuclei can occur. As in chemical reactions, nuclear reactions can either be exothermic (i.e. release energy) or endothermic (i.e. require energy input). Two major classes of nuclear reactions are of importance: fusion and fission . Fusion Fusion is a nuclear process in which two light nuclei combine to form a single heavier nucleus. An example of a fusion reaction important in thermonuclear weapons and in future nuclear reactors is the reaction between two different hydrogen isotopes to form an isotope of helium: 2H + 3H ----> 4He + n This reaction liberates an amount of energy more than a million times greater than one gets from a typical chemical reaction.

Such a large amount of energy is released in fusion reactions because when two light nuclei fuse, the sum of the masses of the product nuclei is less than the sum of the masses of the initial fusing nuclei. Once again, Einstein's equation, E=mc2, explains that the mass that is lost it converted into energy carried away by the fusion products. Even though fusion n is an energetically favorable reaction for light nuclei, it does not occur under standard conditions here on Earth because of the large energy investment that is required. Because the reacting nuclei are both positively charged, there is a large electrostatic repulsion between them as they come together. Only when they are squeezed very close to one another do they feel the strong nuclear force, which can overcome the electrostatic repulsion and cause them to fuse. Fusion reactions have been going on for billions of years in our universe. In fact, nuclear fusion reactions are responsible for the energy output of most stars, including our own Sun. Scientists on Earth have been able to produce fusion reactions for only about the last sixty years. At first, there were small scale studies in which only a few fusion reactions actually occurred. However, these first experiments later lead to the development of thermonuclear fusion weapons (hydrogen bombs).

Fusion is the process that takes place in stars like our Sun. Whenever we feel the warmth of the Sun and see by its light, we are observing the products of fusion. We know that all life on Earth exists because the light generated by the Sun produces food and warms our planet. Therefore, we can say that fusion is the basis for our life. When a star is formed, it initially consists of hydrogen and helium created in the Big Bang, the process that created our universe. Hydrogen isotopes collide in a star and fuse forming a helium nucleus. Later, the helium nuclei collide and form heavier elements. Fusion is a nuclear reaction in which nuclei combine to form a heavier nucleus. It is the basic reaction which drives the Sun. Lighter elements fuse and form heavier elements. These reactions continue until the nuclei reach iron (around mass sixty), the nucleus with the most binding energy. When a nucleus reaches mass sixty, no more fusion occurs in a star because it is energetically unfavorable to produce higher masses. Once a star has converted a large fraction of its core's mass to iron, it has almost reached the end of its life. The fusion chain cannot continue so its fuel is reduced.

Some stars keep shrinking until they become a cooling ember made up of iron. However, if a star is sufficiently massive, a tremendous, violent, brilliant explosion can happen. A star will suddenly expand and produce, in a very short time, more energy than our Sun will produce in a lifetime. When this happens, we say that a star has become a supernova. While a star is in the supernova phase, many important reactions occur. The nuclei are accelerated to much higher velocities than can occur in a fusing star. With the added energy caused by their speed, nuclei can fuse and produce elements higher in mass than iron. The extra energy in the explosion is necessary to over come the energy barrier of a higher mass element. Elements such as lead, gold, and silver found on Earth were once the debris of a supernova explosion. The element iron that we find all through the Earth and in its center is directly derived from both super novae and dead stars. More peaceful uses of fusion are being researched today with the hope that soon we will be able to control fusion reactions to generate clean, inexpensive power. Fission Fission is a nuclear process in which a heavy nucleus splits into two smaller nuclei.

An example of a fission reaction that was used in the first atomic bomb and is still used in nuclear reactors is 235U + n ----> 134Xe + 100Sr + 2n The products shown in the above equation are only one set of many possible product nuclei. Fission reactions can produce any combination of lighter nuclei so long as the number of protons and neutrons in the products sum up to those in the initial fissioning nucleus. As with fusion, a great amount of energy can be released in fission because for heavy nuclei, the summed masses of the lighter product nuclei is less than the mass of the fissioning nucleus. Fission occurs because of the electrostatic repulsion created by the large number of positively charged protons contained in a heavy nucleus. Two smaller nuclei have less internal electrostatic repulsion than one larger nucleus. So, once the larger nucleus can overcome the strong nuclear force which holds it together, it can fission. Fission can be seen as a "tug-of-war" between the strong attractive nuclear force and the repulsive electrostatic force. In fission reactions, electrostatic repulsion wins.

Fission is a process that has been occurring in the universe for billions of years. As mentioned above, we have not only used fission to produce energy for nuclear bombs, but we also use fission peacefully everyday to produce energy in nuclear power plants. Interestingly, although the first man-made nuclear reactor was produced only about fifty years ago, the Earth operated a natural fission reactor in a uranium deposit in West Africa about two billion years ago! Cosmic Rays High energy electrons, protons, and complex nuclei can be produced in a number of astronomical environments. Such particles travel throughout the universe and are called cosmic rays. Some of these particles reach our Earth. As these objects hit our atmosphere, other particles called pions and muons are produced. These particles then slow down or crash into other atoms in the atmosphere. Since the atmosphere slows down these particles, the higher we travel, the more cosmic radiation we see. When you visit the mountains or take an airplane ride, you will encounter more cosmic radiation than if you stayed at sea level. Most cosmic radiation is very energetic. It can easily pass through an inch of lead. Since cosmic radiation can cause genetic changes, some scientists believe that this radiation has been important in driving the evolution of life on our planet.

While cosmic radiation can cause some damage to individuals, it also has played an important role in creating humans. Our atmosphere is naturally shielding us from harmful effects. However, if we were to leave the earth and travel to some planet, we could be subjected to very high levels of radiation. Future space travelers will have to find some way to minimize exposure to cosmic rays. To find out more information, please take a look at experiments (10-14). Cosmic Ray Exercise Turn on the Geiger counter . Use the most sensitive scale. Make sure that no radioactive material is nearby. What do you hear? Every few seconds, you will hear some beeps from the counter. Some of these counts are caused by cosmic rays. Surround the counter by some concrete or iron. Do the counts go away? Take the Geiger counter to a mountain such as Mount Diablo or Mount Tamalpias. Can you measure an increase in rate? It might be necessary to make measurements for five to ten minutes or more to achieve sufficient statistical accuracy.

Properties radiation alpha beta gamma neutrons positron electric charge relative mass radioactivity radiation dangers precautions KS4 science igcse/gcse GCE A Level chemistry physics revision notes IONISING RADIATIONS emitted when unstable atomic nuclei undergo radioactive decay Experiment to show there are at least three types of emissions from radioactive substances. Left to right - alpha particles, gamma rays and beta particles The radioactive emissions become separated in a strong electromagnetic field because alpha particles (+2) and beta particles (-1) have different charges, so go in opposite directions in electric or magnetic fields. Gamma photons (rays of electromagnetic radiation) have no charge (0) and go straight on to the detector (photographic plate, electronic screen, ionisation effect - electronic signal). The beta particles are deflected more because they have a much smaller mass than alpha particles (for more details see table below). Beta particles are so easily deflected that in a magnetic field they might spiral around! Two simple diagrams (above & below) to show the penetration of alpha particle radiation, beta particle radiation and gamma radiation (for more details see table below).

The PROPERTIES of ALPHA, BETA, GAMMA and neutron RADIATIONS The three radiations highlighted are the one you most likely need to know, but maybe the other two as well?

Type of radiation emitted & symbol Nature of the radiation formation, structure, relative mass, electric charge Other nuclear Symbols Penetrating power (and speed), and what will block it (more dense material, more radiation is absorbed BUT smaller mass or charge of particle, more penetrating) Ionising power - the ability to remove electrons from atoms to form positive ions, the process is called ionisation Alpha particle radiation a helium nucleus of 2 protons and 2 neutrons, mass = 4, charge = +2, is expelled at high speed from the nucleus Low penetration , slowest speed (but still ~10% speed of light!), biggest mass and charge, stopped by a few cm of air or thin sheet of paper Very high ionising power , the biggest mass and charge of the three radiation's, the biggest 'punch' in ripping off electrons from molecules, other ions are formed eï¿½ beta minus particle radiation high kinetic energy electrons , mass = 1/1850, charge = -1, expelled when a neutron changes to a proton in the nucleus beta minus, beta ï¿½ Moderate penetration (~90% speed of light), 'middle' values of charge and mass, most stopped by a few mm of metals like aluminium

, will travel quite a few metre in air Moderate ionising power , with a smaller mass and charge than the alpha particle, but still quite good at knocking off electrons from molecules - moderate ionisation e+ beta plus particle emission high KE positive electron called a positron, mass = 1/1850, charge = +1, expelled when a proton changes to a neutron in the nucleus.

beta plus, beta + Theoretically as above, BUT, the positron is the antiparticle of the electron. it is identical to an electron but opposite in charge. Destroyed when it meets an electron (see on right) producing two high energy gamma ray photons, so it doesn't get very far. Theoretically as above, BUT when electron meets positron, kapow ! e+ + eï¿½ ==> 2 high KE actually called annihilation ! very high frequency electromagnetic radiation , mass = 0, charge = 0, gamma emission often accompanies alpha and beta decay Very highly penetrating (100% speed of light !), smallest mass and charge and greatest speed, most stopped by a thick layer of steel or a very thick layer of concrete, but even a few cm of dense lead doesn't stop all of it! gamma rays can pass through many m of air.

The lowest ionising power of the three, gamma radiation carries no electric charge and has virtually no mass, so not much of a 'punch' when colliding with an atom to remove an electron, weak ionisation n neutron radiation neutron, mass = 1, charge = 0, fundamental particle of the nucleus Highly penetrating (more than alpha & beta & sometimes gamma). However, neutrons are most readily absorbed by light nuclei so hydrogen-rich materials like water, poly(ethene) plastic and concrete are used for neutron radiation shielding. The nuclei formed often emit gamma radiation so an extra thick protective layer of lead is needed around a neutron rich environment ! Can't ionise directly, but they are absorbed by the nuclei of atoms they pass through. This can make the atom unstable - radioactive, hence other nuclear radiations may then be produced, producing an 'indirect ionisation' effect. So neutron radiation is as dangerous as any of the others. IMPORTANT NOTE: The emission of an alpha particle or beta particle leads to a change in the composition of a nucleus in terms of protons or neutrons. The emission of a gamma photon does NOT change the composition of the nucleus, it only lowers the energy associated with the nucleus.

Nuclear radiation: The penetration trends and the effects of Ionisation from radioisotopes All radioactive emissions are extremely dangerous to living organisms. All three radiations can penetrate living cells causing damage. The effects of radiation on a living organism depends on the type of radiation and how much of it you are exposed. Sources of ionising radiation are discussed in section 3b. When alpha, beta or gamma radioactive emissions hit living cells they cause ionisation (ionization) effects, and break chemical bonds e.g. in DNA causing molecular damage and destroying vital complex molecules. If powerful enough, ionising radiation can cause burns, kill cells directly or cause genetic damage e.g. to the DNA molecules causing mutations and cancer. So high intense radiation doses cause severe burn effects and can kill cells, and death can result. For thing is for sure, the greater the radiation dose your body receives, the greater the chance of DNA damage and cancer cells developing. But although low radiation doses don't kill the cells, the cells can still be genetically damaged and can still replicate, these mutations can lead to the formation of cancerous cells and tumor development later.

It is the lower dose effects, particularly if exposed to radioactive material over a long period of time, that cause the seemingly minor damage, but may allow mutated cells to survive. Mutant cells can then divide uncontrollably, that is cancer and potentially lethal tumours develop. High doses of radiation kill cells, but the health hazard effects depend on ... how much radiation you are exposed to, the type of radiation you are exposed to, the energy and penetration of the radiation, best to avoid it if at all possible! When alpha, beta and gamma radiation collide with neutral atoms or molecules they knock off electrons and convert them into charged or ionised particles (ions). Positive ions are formed on electron loss and negative ions are formed by electron gain. The positive ions maybe unstable and very reactive and cause other chemical changes in the cell molecules. The 3 radiations have different capacities to cause cell damage. If the radioactive source, a 'radionuclide', gets inside the body the 'danger' order is alpha > beta > gamma. The bigger the mass or charge of the particle, the bigger its ionising impact on atoms or molecule.

BECAUSE for the radiations the order of mass is 4 > 1/1850 > 0, and for electric charge the order is +2 > -1 > 0, i.e. alpha > beta > gamma for both trends in mass and charge. A single alpha particles travelling at 1/10th the speed of light can devastate living cells in relatively small localised area. Much of the beta and gamma (in particular) radiation will actually pass out of the body without damaging cells. If the radioisotope is in the body the radiation impacts directly on cells with the consequences described above. However, if the radioactive source is outside the body, the order danger is reversed to gamma > beta > alpha because the danger order follows the pattern of penetrating power. The smaller the mass and charge the more penetrating the radiation (reverse the order of above). Gamma and beta are the most penetrating and will reach vital organs in the body and be absorbed. Most gamma radiation passes through soft tissue but some is inevitably absorbed by cells. Alpha radiation would not penetrate through clothing or outer skin cells (preferably dead!) and is highly unlikely to reach living cells below the skin.

Beta radiation is quite penetrating into the body, but not as much as gamma rays. Because of the dangers of this ionising or atomic radiation, all workers and medical staff who are likely to be near radioactive or ionising sources must wear lapel radiation badges containing photographic film to monitor their exposure to radiation. The film is regularly developed and the darker the film the more radiation would have impacted on the person. From the film exposure it is possible to estimate the dose of radiation the individual has received. This is just one examples of tackling the health & safety issues when dealing with radioisotopes. Examples of precautions taken when handling radioactive materials or dealing with ionising radiation include ... Radiographers wear lead lined aprons and anyone else involved in radiotherapy cancer treatment must take particular precautions and radiation monitored. Radiographers who work in hospitals with ionising radiation (gamma or X-rays, CT scanning) have higher risk of exposure above background radiation. Radiographers wear lead aprons and/or stand behind protective lead/lead glass screens in another room to work as remotely as possible to minimise their radiation dose. Everything can now be done at a safe distance and the dangers from prolonged exposure to ionising radiation are virtually eliminated now.

when X-rays were first used for X-raying bones in the early 20th century, almost all of the first generation of radiographers died early from cancer! If someone is having an X-ray or radiotherapy for cancer, apart from the area of the body under examination or treatment, the rest of the body should be protected with a lead or other radiation absorbing material, again to minimise the patient's overall radiation dose. Uranium miners and nuclear power workers are exposed to much higher levels of radiation than background radiation ( discussed in 3b. ) Such workers need to wear face masks, protective clothing (specifically designed suite and gloves) to prevent touching or inhaling dust from radioactive materials. These workers should be wearing radiation badges, and after a work shift, be thoroughly showered and checked for any radioactive contamination and regular health checks. Deep in underground mines ionising radiation levels are higher because of radioactive-isotopes in the surrounding rocks. In nuclear fuel preparation and reprocessing, as much work is done using robotic control systems from behind steel, concrete, lead or thick lead glass panels for visual monitoring of the situation. Lead is very good absorber of all types of radiation, but a thick layer in needed to stop all the gamma radiation.

Small samples of radioisotopes can be stored in a lead-lined box which should be brought out for the minimum of time and stored safely way in a secure room that is not used for any other purpose. All radioactive materials (weakly or strongly emitting) must be handled and processed with the greatest of care. There should be minimum contact time in handling radioactive materials so exposure is at a minimum. There should NEVER be any contact of your skin with radioactive materials, which is why remotely-controlled robotic arms are frequently used to avoid the dangers of contact with radioactive materials. Always handle containers of radioisotopes with gloves and tongs if possible and at arms length. Increasing the distance between you and the radioactive source reduces exposure and alpha particles are absorbed by a few cm of air. In research laboratories, experiments are conducted in sealed fume cupboards at the laboratory side and technicians work through sealed whole arm gloves through a thick lead glass front. You can also reduce the pressure in the fume cupboard so there is no chance of pressure leakage out into the laboratory area. No skin contact with any radioactive materials or bring the face anywhere near to the source. Handle sample containers with tongs at arm's length.

All radioisotopes are kept in thick lead-lined containers, suitably labelled with the hazard warning symbol for radioactive materials. Industrial and research workers may need to wear a full protective suit to prevent any, even microscopic, radioactive particles to come into contact with the skin or inhaled into the lungs. Thick lead/steel/concrete barriers, even lead-lined suits are needed to protect people from deadly deeply penetrating gamma radiation, though alpha and beta radiations are less penetrating. At high altitude the background radiation increases so commercial airline pilots are greater risk from the dangers of cosmic rays (some even higher energy than gamma rays). I don't know if any precautions are taken? - Beta | definition of beta by Medical dictionary Beta | definition of beta by Medical dictionary beta [ba´tah] second letter of the Greek alphabet, β; used to denote the second position in a classification system. Often used in names of chemical compounds to distinguish one of two or more isomers or to indicate the position of substituent atoms or groups in certain compounds.

Also used to distinguish types of radioactive decay; brain rhythms or waves; adrenergic receptors; secretory cells of the various organs of the body that stain with basic dyes, such as the beta cells of the pancreas; and the type of hemolytic streptococci that produce a zone of decolorization when grown on blood media. beta-adrenergic blocking agent (beta-blocker) any of a group of drugs that block the action of epinephrine at beta-adrenergic receptors on cells of effector organs. There are two types of these receptors: β1-receptors in the myocardium and β2-receptors in the bronchial and vascular smooth muscles. The principal effects of beta-adrenergic stimulation are increased heart rate and contractility, vasodilation of the arterioles that supply the skeletal muscles, and relaxation of bronchial muscles. Because of their effects on the heart, these agents are used to treat angina pectoris , hypertension, and cardiac arrhythmias . And, because they decrease the workload of the heart, they are effective in reducing the long-term risk of mortality and reinfarction after recovery from the acute phase of a myocardial infarction .

They are an important adjunct in treatment of heart failure and are also used for prophylaxis of migraine. Nonselective beta-adrenergic blocking agents affect both types of receptors and can produce bronchospasm in patients with asthma or chronic obstructive pulmonary disease. If such patients need one of these drugs, they should be given a cardioselective one that preferentially blocks the β1-receptors in the heart. Nonselective agents include propranolol ( Inderal ), used for treatment of angina, hypertension, arrhythmias, and migraine and for prophylaxis after the acute phase of a myocardial infarction; nadolol ( Corgard ), used for treatment of angina and hypertension; and timolol , used as an ophthalmic preparation ( Timoptic ) for treatment of glaucoma and as an oral preparation ( Blocadren ) for treatment of hypertension and for prophylaxis after the acute phase of a myocardial infarction. Cardioselective beta-adrenergic blocking agents are used for treatment of hypertension and include atenolol ( Tenormin ) and metoprolol ( Lopressor ).

beta particles negatively charged particles emitted by radioactive elements, the result of disintegration of neutrons; their source is the unstable atoms of radioactive metals such as radium and uranium. There are three general types of emissions from radioactive substances: alpha and beta particles and gamma rays. Beta particles are less penetrating than gamma rays and may be used to treat certain conditions on or near the surface of the body. See also radiation and radiation therapy . β In typography, do not substitute the German compound letter β for this Greek letter. 1. Second letter of the Greek alphabet, beta. 2. chemistry denotes the second in a series, the second carbon from a functional (for example, carboxylic) group, or the direction of a chemical bond toward the viewer. For terms having this prefix, see the specific term. 3. Pressure coefficient. be·ta (β), (bā'tă), In typography, do not substitute the German compound letter β for the Greek letter β. Second letter of the Greek alphabet, β (see entry at start of letter "Bs.") [G.] /β/ (beta, the second letter of the Greek alphabet) β chain of hemoglobin.

beta /be·ta/ (ba´tah) β, the second letter of the Greek alphabet; see also β-. beta [bē′tə, bā′tə] B, β, the second letter of the Greek alphabet, used in scientific notation to denote position of a carbon atom in a molecule, a type of protein configuration, or identification of a type of activity, as beta blocker, beta particle, or beta rhythm. It is used in statistics to define an error in the interpretation of study results. beta Medspeak The second letter in the Greek alphabet. The term is included here to flag the differences in pronunciation between British and American English. Medspeak-UK: pronounced, BEE tuh. Statistics The probability of a Type-II false-negative error. In hypothesis testing, beta is the probability of concluding incorrectly that an intervention is not effective when it has true effect. 1-b is the power to detect an effect of an intervention if one truly exists beta β The second letter of the Greek alphabet; Statistics The probability of a Type II–false-negative error. See Type II error . Cf Alpha . β

Question: Which letter from the Greekalphabet is the symbol of the most penetrating type of radiation containing no particles ?
Answer: GAMMA