A heavy nucleus Q of half-life 20 minutes undergoes alpha-decay with probability of 60% and beta-decay with probability of 40%. Initially, the number of Q nuclei is 1000. The number of alpha-decays of Q in the first one hour is
(A) 50 (B) 75 (C) 350 (D) 525 Continue reading A heavy nucleus Q of half-life 20 minutes …
The half-life of a radioactive nuclide is 100 hours. The fraction of original activity that will remain after 150 hours would be:
(1) $\frac {1}{2}$ (2) $\frac {1}{2\sqrt 2}$
(3) $\frac {2}{3}$ (4) $\frac {2}{3\sqrt 2}$ Continue reading The half-life of a radioactive nuclide is 100 hours ….
A radioactive nucleus ${}_Z^AX$ undergoes spontaneous decay in the sequence ${}_Z^AX \to {}_{Z – 1}B \to {}_{Z – 3}C \to {}_{Z – 2}D$ where Z is the atomic number of element X. The possible decay particles in the sequence are:
(1) $\alpha,\beta^-.\beta^+$
(2) $\alpha,\beta^+,\beta^-$
(3) $\beta^+,\alpha,\beta^-$
(4) $\beta^-,\alpha,\beta^+$ Continue reading A radioactive nucleus ${}_Z^AX$ undergoes ….
A nucleus with mass number 240 breaks into two fragments each of mass number 120, the binding energy per nucleon of unfragmented nucleus is 7.6 MeV while that of fragments is 8.5 MeV. The total gain in the binding energy in the process is:
(1) 0.9 MeV
(2) 9.4 MeV
(3) 804 MeV
(4) 216 MeV Continue reading A nucleus with mass number 240 breaks into ….
The half life period of radioactive element x is same as the mean life time of another radioactive element y. Initially they have the same number of atoms. Then:
(A) x and y have same decay rate initially and later on different decay rate.
(B) x and y decay at the same rate always.
(C) x will decay faster than y.
(D) y will decay faster than x.
Solution
Given, ${({t_{1/2}})_x} = {({t_{mean}})_y}$
$\therefore \frac{{0.693}}{{{\lambda _x}}} = \frac{1}{{{\lambda _y}}}$
$ \Rightarrow {\lambda _x} = 0.693{\lambda _y}$
$ \Rightarrow {\lambda _x} < {\lambda _y}$
If N is same, $A \propto \lambda $
$\therefore A_x < A_y $
Answer: (D)
