Physics Test – Nuclear Physics – S2T3

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What is meant by a radioactive substance?
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If an atom is radioactive it means it emits ionizing radiation or particles. When the binding force of the nucleus is not strong enough, it is unstable (therefore radioactive).
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What is meant by the term, “isotope” and what happens to unstable isotopes when they decay?
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An isotope is the same element (so the same # of protons) with different numbers of neutrons. When an atom is unstable to become more stable, it will give off particles and/or energy such as alpha, beta, or gamma radiation.
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What is meant by the “half-life” of a radioactive sample?
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The half life of a radioactive isotope is the average time it takes for the number of nuclei of the isotope in the sample to halve.
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A radioactive sample of iodine-131 give a count rate of 1200 counts per second. The half-life of iodine-131 is 8 days. How many days will it take for the sample count rate to fall to 75 counts per second?
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??
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What is the half-life of the radioactive sample shown in the graph (see answer for picture)
What is the half-life of the radioactive sample shown in the graph (see answer for picture)
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2 hours is the half-life
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Which type of nuclear radiation is most ionizing and has the lowest range in air?
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Alpha
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Which type of nuclear radiation is the least ionizing and has the greatest range in air?
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Gamma
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What is required to stop beta radiation?
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aluminum 5mm thick or a few meters in air
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Inside a radiation badge there are sections with small sheets of copper, aluminium, and lead, why is this?
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It is so they can test which types of radiation are present, and how much of the radiation there is.
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Explain what is meant by ionizing radiation
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Ionizing power is the ability of different types of radiation to cause atoms to lose electrons and therefore form ions.
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Explain why ionizing radiation is dangerous
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It changes the atom’s composition, knocking electrons out of atoms and making them charged. When atoms in living cells become ionized, they usually either die, repair themselves, or mutate incorrectly and can become cancerous.
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Explain what happens to gamma radiation in magnetic or electric field – draw if it helps.
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Nothing because gamma radiation doesn’t have a charge.
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How does the path change for a charged particle in a magnetic field? Give an example.
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The positive charges would be directed toward the negative part of the magnetic field and visa verse. If beta radiation was in a magnetic field it would flow to the positive side.
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Explain how you could use a geiger-muller counter to test the range of different types of nuclear radiation.
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The nuclear radiation ionizes that gas inside the tube, therefore, with the ions formed a flow of charge can momentarily flow through this path completing the circuit and therefore counting the presence of nuclear radiation.
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Would a geiger-muller counter work if the tube had no gas in it (a vacuum)?
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No, because there would be nothing to ionize, and therefore nothing to form a charge. You need it to close the circuit.
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Would a gamma source be suitable for automatic thickness monitoring of aluminium foil? Explain your answer?
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No, because it passes straight through aluminum.
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Beta radiation can be stopped by Aluminium. Why can it be used for monitoring thickness of aluminium foil?
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Because it can only be stopped by 5mm of aluminum. Variations in thickness of aluminum would show how much radiation is exposed.
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Why is an alpha source most appropriate for use in a smoke detector?
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It is the easiest to block. The smoke easily blocks the radiation, so the alarm goes off.
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Explain how the age of an igneous rock can be determined by Uranium dating?
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Many rocks contain Uranium in them. By measuring the amount of Uranium-238 and lead-206, you can determine how old the rock is. uranium decays into lead. Because we know the half life of uranium, we can calculate how old it is.
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Why would the age of rock not be possible to determine using a radioactive isotope with a half-life of 15 hours?
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If the half-life was that short, you wouldn’t be able to measure anything that was very old at all because the amount of the radioactive substance would be so (SO) small.
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Explain why nuclear radiation can be dangerous?
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When atoms in living cells become ionized , one of 3 things happen: the cell dies, the cell repairs itself, or the cell mutates incorrectly and can become cancerous.
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Explain why a radioactive gamma source with a half life of 6 hours is suitable for medical imaging as a tracer.
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You don’t want someone to intake a radioactive substance with a long half life because then you would walk around radiating dangerous radiation. You want to trace it through the body, and then not need to worry about it again. The radiation also passes easily through many substances. Gamma penetrates through the body.
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What are nucleons?
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Neutrons and protons are called nucleons since they form the atomic nucleus.
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Describe the strong nuclear force and its connection to the stability of an atom’s nucleus.
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The binding energy is found form the Einstein equation E = mc^2. Many details about the nuclear strong force are not yet known, but we do know that it is a very short-range attractive force. It does not exist outside the nucleus. Within a nucleus, protons attract other protons, neutrons attract other neutrons, and they attract one another.
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Which of the following spontaneous reactions exemplifies alpha decay? Explain why.
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Alpha decay occurs when an alpha part ice (a helium nucleus 4 2 HE) is ejected from the nucleus of a parent atom. This also results in a relative mass reduced by 4 and an atomic number reduced by 2.
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Which of the following spontaneous reactions exemplifies beta decay? Explain why.
Which of the following spontaneous reactions exemplifies beta decay? Explain why.
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The atomic # is increased by one. Free neutrons decay into a proton, an electron, and a subatomic particle called an antineutrino (Ve).
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Which of the following spontaneous reactions exemplifies gamma decay? Explain why.
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There is no mass or other charge, only the wave release.
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A sample of 300 grams of a radioactive isotope with half-life of 10 years decays for 50 years. The time period for the decay is equivalent to ___________.
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5 half lives
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A sample of 300 grams of a radioactive isotope with half-life of 10 years decays for 50 years. Calculate how much of the original isotope will remain at the end of the 50 year period.
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1/32*300= 9.375grams ?
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Nuclear fission is a process in which
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??
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Nuclear fusion is a process in which
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All of the above: Extremely high temperatures are required, light nuclei collide at high speed, and light nuclei loose mass and release energy.
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Who is known as the “father of the atomic bomb”?
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J. R. Oppenheimer
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What is nuclear fusion?
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When nuclei collide at high speeds and fuse together
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The sun is powered by fission or fusion?
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fusion
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Does fusion or fission power hydrogen bombs?
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fusion
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Is fission or fusion used in atomic bombs?
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fission
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Who invented the neutron bomb?
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Sam Cohen
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Who discovered x rays?
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Wilhem Conrad Rontgen
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What was one way x rays were “misused?”
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shoe fitting
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who was the first casualty of x ray radiation?
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Clarence Madison Dally in 1900.
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X-ray
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an electromagnetic wave of high energy and very short wavelength, which is able to pass through many materials opaque to light.
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Electromagnetic spectrum
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a continuum of all electromagnetic waves arranged according to frequency and wavelength
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List the types of mutations
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Deletion, Insertion, Substitution, Inversion, Reciprocal translocation
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Deletion
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remove segment of DNA
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Insertion
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add segment of DNA
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Substitution
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a particular base is replaced with 1 other 3 nucleotide base
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Reciprocal traslocation
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excision of segments from 2 non-homologous chromosomes. These portions are inserted into other chromosomes. i.e. Chromosome 1 will gain the section from Chromosome 2 and Chromosome 2 will gain the section from Chromosome 1.
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Mutation (natural)
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change in genome of organisms caused by normal recombination and segregation
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Mutagenesis
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inducing mutations within organisms’ genome
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What 2 scientists did early work on mutagenesis (separately).
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Muller & LJ Stadler
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Name 4 things to know before you experiment with mutagenesis
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1. Safety is a major concern 2. Know the mutation type and mechanisms of your experimental tissue 3. Have tissue specific reactions 4. Know how your species and ploidy levels affect mutation response to the mutagen.
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What equation gives the amount of energy contained within matter?
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E=mc^2
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What is the most commonly used fuel for nuclear reactors?
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Uranium-235
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What is a common absorber of neutrons used in control rods?
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Boron-10
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Fission
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the splitting of larger unstable atoms into smaller atoms into smaller mores stable atoms through releasing neutrons and radiations in the process.
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Fusion
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the merging of small atoms into larger atoms creating heat
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If an object has a mass of 10 kg, how much energy does it have?
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E = 10*(3*10^8)^2 E = 9*10^17 Joules
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What year were the clean air acts passed?
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1970
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What are two negative things about getting energy form fossil fuels?
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Air pollution and Greenhouses gases
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List one negative effect of air pollution:
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Disease
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True or False: Greenhouse gas has the same effects as pollution.
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False (greenhouse gasses are worse)
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How did the citizens of America bring awareness to the bad air in big cities?
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Protest (media coverage)
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What is a commonly used fossil fuel that causes pollution?
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Coal & oil
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What is the atomic number and mass of Americium?
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Atomic #: 95. Atomic Mass: 243 a
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How is Americium formed of what does it decays into?
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Americium forms from the compilation of Plutonium and neutrons with a nuclear reactor; deteriorates into Neptunium.
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What types of radioactive emissions create the electrical current necessary to detect smoke?
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Alpha particles & gamma radiation
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What specifically does the Americium alarm detect, and why is it a liability?
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Americium detects smoke; however, when smoke is detected, the fires will spread within a matter of minutes.
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How is the Photoelectric alarm better than the Americium alarm?
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The reflection of light immediately warns of a possible fire
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How much Americium does a detector require with the half life of 432 years?
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0.29 micrograms
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nuclear medicine
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A branch of medicine that uses radioactive substances in either research, treatments, or diagnosing.
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What are the three types of radiation therapy?
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External, internal, and systematic
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List 2 of the 5 characteristics scientists look at for choosing a radionuclide
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1. a half-life greater than the time to prepare for injection and longer than the examination 2. low toxicity 3. suitable chemical form and reactivity 4. photon energy between 50 and 500 keV (kiloelectron volts) 5. stability or near-stability of the product
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External radiation therapy
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uses high-energy x-ray beams targeted at a patient’s tumor. These beams are generated by a linear accelerator, targeted to destroy the cancer cell while sparing the surrounding tissue.
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In systematic radiation therapy, the radio-pharmaceuticals are bound to what?
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anti-bodies
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internal radiation therapy
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uses a radiation sources that is placed within a small implant which is placed very close to or even inside the tumor so it harms as few healthy cells as possible.
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Alpha radiation
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symbol: α range in air: 5 cm stopped by: thin paper ionizing ability: strong
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Beta radiation
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symbol: β range in air: 1 m stopped by: aluminum (few mm) ionizing ability: moderate
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Gamma radiation
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symbol: Îł range in air: unlimited stopped by: cms of lead OR 1 m of concrete ionizing ability: weak

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