accurate for estimating the age of materials more than 50,000 years old? This form of radioactive dating is only accurate back 1,400 years. Correct! The concentration of carbon-14 in a body after 50,000 years is too low. Living organisms are too decomposed after 50,000 years. Actually, carbon-14 dating is accurate back to around 5 million years ago. Question 27 0 / 1 pts Which type of radiationÑalpha, beta, or gammaÑresults in the least change in atomic number? You Answered alpha radiation beta radiation Correct Answer gamma radiation They all result in the same change in atomic mass number. Question 28 0 / 1 pts Which type of radiationÑalpha, beta, or gammaÑresults in the greatest change in atomic mass number? gamma radiation You Answered beta radiation Correct Answer alpha radiation They all result in the same change in atomic mass number. Question 29 1 / 1 pts When food is irradiated with gamma rays from a cobalt-60 source, does the food become radioactive? Why? Yes. This is why irradiation with cobalt-60 is no longer approved by the FDA. Yes. However, the radioactivity resulting is well below the danger level established by the FDA. Correct! No. The gamma rays do not have sufficient energy to initiate a nuclear reaction in the atoms of the food. Yes and No. Although the gamma rays initiate the nuclear reaction the radioactivity does not show up until the food is ingested. Question 30 1 / 1 pts What evidence supports the contention that the strong nuclear force is stronger than the electrical interaction at short inter-nuclear distances? Correct! Protons are able to exist side-by-side within an atomic nucleus. Neutrons spontaneously decay into protons and electrons. Uranium deposits are always slightly warmer than their immediate surroundings. The radio interference that arises adjacent to any radioactive source. Question 31 1 / 1 pts How can a half-life be used to tell the age of a sample? The half-life of an isotope is constant. The amount of radioactive form depends on the amount of radiation in the surroundings. The ratio between the radioactive form and the stable form depends on the archaeological record. Correct! The ratio between the radioactive form and stable form varies regularly with time. Question 32 0 / 1 pts If a material has a half-life of 24 hours, how long do you have to wait until the amount of radioisotope is 1/4 its original amount? You Answered 12 hours 24 hours Correct Answer 48 hours 72 hours practically forever, but it may be safe by then Question 33 0 / 1 pts Why does plutonium not occur in appreciable amounts in natural ore deposits? Most naturally occurring plutonium deposits have already been depleted in the creation of nuclear weapons. You Answered Plutonium is strictly a human-made element. Correct Answer Any plutonium initially in the earth's crust has long since decayed. Plutonium loses electrons to form positively charged particles that have long since washed into the oceans. Question 34 0 / 1 pts Is it at all possible for a hydrogen nucleus to emit an alpha particle? You Answered yes, because alpha particles are the simplest form of radiation no, because it would require the nuclear fission of hydrogen, which is impossible yes, but it does not occur very frequently Correct Answer no, because it does not contain enough nucleons Question 35 0 / 1 pts What property of half-lives makes radioactive material so problematic? (A) There is no known way to shorten a half-life. (B) Radioactivity is determined by the natural decay-time to stable isotopes. You Answered (C) All half-lives are long. (D) There is no known way to measure half-lives with any accuracy. Correct Answer both A and B Question 36 1 / 1 pts What is the main technical difficulty in dealing with fusion reactions? Correct! The amount of energy needed to overcome the electrical repulsion of the reactants is extremely high. The reactants are highly toxic and extremely radioactive. The mass of the reactants is less than the mass of the products. It isn't possible to artificially generate the conditions needed for fusion. Question 37 0 / 1 pts Carbon-14 dating is fairly reliable for dating once-living materials that died up to ________. You Answered 5000 years ago Correct Answer 50,000 years ago 250.000 years ago 2.5 million years ago Question 38 0 / 1 pts The alpha particle has twice the electric charge of the beta particle but deflects less than the beta in a magnetic field because it ________. You Answered moves much slower moves much faster Correct Answer is more massive has much less mass Question 39 1 / 1 pts Why doesn't uranium ore spontaneously undergo a chain reaction? Uranium ore must be "weapons' grade" in order for it to undergo chain reaction. Correct! Uranium ore is mostly non-fissionable isotope U-238. Uranium ore does spontaneously undergo slow chain reaction over time finally resulting in it becoming lead. Uranium ore, mostly U-235, must be enriched with U-238 in order for it to undergo a chain reaction. Question 40 0 / 1 pts A certain radioactive element has a half-life of one hour. If you start with a 1-g sample of the element at noon, how much of this same element will be left at 3:00 PM? You Answered 0.5 gram 0.25 gram Correct Answer 0.125 gram 0.0625 gram Question 41 1 / 1 pts Which process would release energy from gold, fission or fusion? From carbon? gold: fusion; carbon: fission gold: fission; carbon: fission Correct! gold: fission; carbon: fusion gold: fusion; carbon: fusion Question 42 1 / 1 pts The age of the Dead Sea Scrolls was found by carbon-14 dating. Could this technique have worked if they were carved in stone tablets? Explain. Yes, because there are appreciable levels of carbon even in stone. Correct! No, this method of dating requires a material that was once living. Yes, because X-ray images could be collected instead. No, the stones in the arid environment of the Dead Sea would have lost all of their carbon-14 by now. Question 43 0 / 1 pts Which of the following elements is the most stable from a nuclear point of view? You Answered argo hydrogen Correct Answer iron uranium Question 44 0 / 1 pts Which of the following provides the minimum amount of protection you need to block the following form of radiation? alpha You Answered lead suit Correct Answer suntan lotion thick leather T-shirt Question 45 1 / 1 pts The isotope Cesium-137, which has a half-life of 30 years, is a product of nuclear power plants. How long will it take for this isotope to decay to about one-sixteenth its original amount? 480 years 240 years Correct! 120 years 960 years Question 46 1 / 1 pts Just after an alpha particle leaves the nucleus, would you expect it to speed up? Why? No. Once the alpha particle leaves the nucleus it is slowed by the repulsion of the next closest atom's nucleus. No. As the alpha particle leaves the nucleus it is slowed by the constant attraction of the electrons surrounding the nucleus. Yes. Once the alpha particle leaves the nucleus there are no more forces acting on it and it therefore accelerates. Correct! Yes. Once the alpha particle leaves the nucleus it accelerates because of mutual electric repulsion with the nucleus from which it escaped. Question 47 0 / 1 pts Which of the following statements about chain reactions is true? Only uranium isotopes are capable of supporting a chain reaction. You Answered Three or more neutrons must be released to sustain a chain reaction. Correct Answer It requires that more neutrons are produced than are absorbed. It is not possible to stop or control a chain reaction once it has been started. Question 48 0 / 1 pts Is the mass of an atomic nucleus greater or less than the sum of the masses of the nucleons composing it? Why don't the nucleon masses add up to the total nuclear mass? Greater. We need to add the masses of the surrounding electrons to the masses of the nucleons. You Answered Neither. The mass of the atomic nucleus is exactly the sum of the masses of the nucleons. Correct Answer Less. The individual nucleons have greater mass when separated from the nucleus. This additional mass is a result of the energy of separation. Greater. The mass of the atomic nucleus also has mass of the "atomic glue" that holds the nucleons together in the nucleus. Question 49 1 / 1 pts Which of the following statements about fission is true? Correct! The amount of energy released in the fission of large nuclei is very large. The amount of energy released in the fusion of small nuclei is very large. Bombarding a nucleus with neutrons always leads to fission. The fragments of a fusion reaction are always the same size. Question 50 1 / 1 pts Radioactivity is a tendency for an element or a material to ________. Correct! emit radiation emit light emit electrons glow in the dark