# Class 10 Physics Atomic and Nuclear Physics 18.2. What nuclear reaction would release more energy the fission reaction or the fusion reaction? Explain.

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##### 18.2. What nuclear reaction would release more energy the fission reaction or the fusion reaction? Explain.

18.9. What is meant by background radiations? Enlist some sources of background radiations.

18.4. What is the difference between natural and artificial radioactivity?

18.7. What do you understand by half-life of a radioactive element?

18.12. Complete this nuclear reaction: { }_{92}^{2 s} U \longrightarrow{ }_{54} X+?+2{ }_{5} \mathrm{n} . Does this react involve fission or fusion? Justify your answer.

vii. Release of energy by the Sun is due to(a) nuclear fission(b) nuclear fusion(c) burning of gases(d) chemical reaction

18.7. How much of a 1 \mathrm{~g} sample of pure radioactive substance would be left undecayed after four half-lives?

18.8. Half-life of a radioactive element was found to be 4000 years. The count rates per minute for 8 successive hours were found to be 270280300310285290305 312. What does the variation in count rates show? Plot a graph between the count rates and time in hours. Why the graph is a straight line rather than an exponential?

18.9. What information about the structure of the nitrogen atom can be obtained from its nuclide { }_{7}^{14} N ? \mid n what way atom in { }_{7}^{14} N is different from the atom in { }_{7}^{16} N ?

18.1. The half-life of { }_{7}^{16} N is 7.3 \mathrm{~s} . A sample of this nuclide of nitrogen is observed for 29.2 \mathrm{~s} . Calculate the fraction of the original radioactive isotope remaining after this time.Ans. (1/16)

viii. When a heavy nucleus splits into two lighter nuclei the process would(a) release nuclear energy(b) absorb nuclear energy(c) release chemical energy(d) absorb chemical energy

18.1. Is it possible for an element to have different types of atoms? Explain.

18.5. Half-life of a radioactive element is 10 minutes. If the initial count rate is 368 counts per minute find the time for which count rates reaches 23 counts per minute.Ans. (40 minutes)

18.8. Is radioactivity a spontaneous process? Elaborate your answer with a simple experiment.

v. The half-life of a certain isotope is 1 day. What is the quantity of the isotope after 2 days?(a) one-half(b) one-quarter(c) one-eighth(d) none of these

Example 18.3: A radioactive element has a half-life of 40 minutes. The initial count rate was 1000 per minute. How long will it take for the count rate to drop to (a) 250 per minutes (b) 125 per minutes (c) Plot a graph of the radioactive decay of the element.

18.5. Write the alpha decay process for { }_{91}^{234} P a . Identify the parent and daughter nuclei in this decay.

18.13. Nuclear fusion reaction is more reliable and sustainable source of energy than nuclear fission chain reaction. Justify this statement with plausible arguments.

18.4. Technetium-99 \mathrm{m} is a radioactive element and is used to diagnose brain thyroid liver and kidney diseases. This element has half-life of 6 hours. If there is 200 \mathrm{mg} of this technetium present how much will be left in 36 hours.Ans. (3.12mg)

18.2. What do you mean by the term radioactivity? Why some elements are radioactive but some are not?

18.6. In an experiment to measure the half-life of a radioactive element the following results were obtained:\begin{tabular}{|cccccc|}\hline Count rate / minute & 400 & 200 & 100 & 50 & 25 \\Time (in minutes) & 0 & 2 & 4 & 6 & 8 \\\hline\end{tabular}Plot a graph between the count rate and time in minutes. Measure the value for the half-life of the element from the graph.Ans. (half-life is 2 minutes)

18.3. Which has more penetrating power an alpha particle or a gamma ray photon?

Example 18.2: The activity of a sample of a radioactive bismuth decreases to one-eight of its original activity in 15 days. Calculate the half-life of the sample.

18.6. Explain whether the atomic number can increase during nuclear decay. Support your answer with an example.

Example 18.1: Find the number of protons and neutrons in the nuclide defined by { }_{6}^{13} X .

18.1. What is difference between atomic number and atomic mass number? Give a symbolical representation of a nuclide.

18.2. Cobalt-60 is a radioactive element with half-life of 5.25 years. What fraction of the original sample will be left after 26 years?Ans. (1/32)

18.11. What are two common radiation hazards? Briefly describe the precautions that are taken against them.

18.14. A nitrogen nuclide { }_{7}^{14} N decays to become an oxygen nuclide by emitting an electron. Show this process with an equation.