Problem 124
Which of the following statements is/are incorrect, when the nuclide, \({ }_{19} \mathrm{~K}^{40}\), is subject to \(\mathrm{K}\)-electron capture? (a) \({ }^{40} \mathrm{Ar}\) is produced with emission of \(\beta\)-particle. (b) \({ }^{40} \mathrm{Ar}\) is produced with emission of \(\alpha\)-particles. (c) \({ }^{40} \mathrm{Ar}\) is produced without emission of radiation (d) \({ }^{40} \mathrm{Ar}\) is produced with emission of X-radiation.
Problem 125
An unstable nucleus is characterized by (i) \(\mathrm{n} / \mathrm{p}>1\) (ii) low binding energy (iii) high temperature and pressure (iv) high packing fraction (a) (i), (ii) (b) (i), (ii), (iv) (c) (i), (ii), (iii) (d) (i), (ii), (iii), (iv)
Problem 127
How much time is required for a \(5.75\)-mg sample of \({ }^{51} \mathrm{Cr}\) to decay to \(1.50 \mathrm{mg}\) if it has a half-life of \(27.8\) days? (a) \(5.39\) days (b) \(2.69\) days (c) \(53.9\) days (d) \(5.49\) days
Problem 128
Potassium \(-40\) decays to argon \(-40\) with a half life of \(1.27 \times 10^{9} \mathrm{yr}\). What is the age of a rock in which the mass ratio of \({ }^{40} \mathrm{Ar}\) to \({ }^{40} \mathrm{~K}\) is \(3.6\) ? (a) \(2.8 \times 10^{10} \mathrm{yr}\) (b) \(1.4 \times 10^{9} \mathrm{yr}\) (c) \(1.4 \times 10^{10} \mathrm{yr}\) (d) \(2.8 \times 10^{9} \mathrm{yr}\)
Problem 130
What should be the age of fossil for meaningful determination of its age? (a) 6 years (b) 6000 years (c) 60,000 years (d) It can be used to calculate any age
Problem 133
Match the following $$ \begin{array}{ll} \hline \text { Column-I (Reactions) } & \begin{array}{l} \text { Column-II } \\ \text { (Particles) } \end{array} \\ \hline \text { (a) }{ }_{4} \mathrm{Be}^{9}+{ }_{2} \mathrm{He}^{4} \rightarrow{ }_{6} \mathrm{C}^{12}+\ldots \ldots & \text { (p) }{ }_{2} \mathrm{He}^{4} \\ \text { (b) }{ }_{6} \mathrm{C}^{12}+\ldots \ldots \rightarrow{ }_{5} \mathrm{~B}^{10}+{ }_{2} \mathrm{He}^{4} & \text { (q) }{ }_{0} \mathrm{n}^{1} \\\ \text { (c) }{ }_{7} \mathrm{~N}^{14}+\ldots \ldots \rightarrow{ }_{8} \mathrm{O}^{17}+{ }_{1} \mathrm{H}^{1} & \text { (r) }{ }_{1} \mathrm{D}^{2} \\\ \text { (d) }{ }_{20} \mathrm{Ca}^{40}+\ldots \ldots \rightarrow{ }_{19} \mathrm{~K}^{37}+{ }_{2} \mathrm{He}^{4} & \text { (s) }_{1} \mathrm{H}^{1} \\\ \hline \end{array} $$
Problem 134
Match the following Column-I (a) \(\mathrm{P}^{32}\) (b) \(\mathrm{Na}^{24}\) (c) \(\mathrm{Co}^{60}\) (d) \(I^{131}\) Column-II (p) Location of tumour in the brain (q) Location of blood clots and circulatory disorders (r) Radiotherapy (s) Agricultural research
Problem 135
Match the lists I and II and pick the correct matching from the codes given below, Column-I (a) Isotope (b) Isobar (c) Isotone (d) Isosters (e) Isodiaphers Column-II (p) \({ }_{88} \mathrm{Ra}^{228}\) and \({ }_{89} \mathrm{Ac}^{228}\) (q) \({ }_{18} \mathrm{Ar}^{39}\) and \({ }_{19} \mathrm{~K}^{40}\) (r) \({ }_{1} \mathrm{H}^{2}\) and \({ }_{1} \mathrm{H}^{3}\) (s) \({ }_{92} \mathrm{U}^{235}\) and \(_{90}^{\mathrm{Th} 231}\) (t) \(\mathrm{CO}_{2}\) and \(\mathrm{N}_{2} \mathrm{O}\)
Problem 136
A fresh radioactive mixture containing short lived species \(X\) and \(Y\). Both the species together emitting \(8000 \alpha\) - particles per minute initially. 20 minutes later \(X\) was emitting \(\alpha-\) particles at the rate of 4500 per minute. If the half lives of the species \(\mathrm{X}\) and \(\mathrm{Y}\) are 10 minute and 500 hours, then what is the ratio of initial activities of \(X\) and \(Y\) in the mixture?
Problem 137
The disintegration rate of a certain radioactive sample at any instant is \(5400 \mathrm{dpm}\). After 5 min the rate becomes \(2700 \mathrm{dpm}\). The half life of the sample in min is approximately
