If the nuclear radius of ${}_{27}Al$ is 3.6 Fermi, the approximate nuclear radius of ${}_{64}Cu$ in Fermi is

(a)2.4                                         (b)1.2

(c)4.8                                         (d)3.6

Concept Questions :-

Mass-energy equivalent
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Difficulty Level:

A mixture consists of two radioactive materials ${A}_{1}$ and ${A}_{2}$ with half lives of 20 s and 10 s respectively.Initially the mixture has 40g of ${A}_{1}$ and 160g of ${A}_{2}$. The amount of the two in the mixture will become equal after

(a)60 s                                      (b)80 s

(c)20 s                                      (d) 40 s

Concept Questions :-

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Difficulty Level:

The half life of a radioactive nucleus is

50 days. The time interval $\left({\mathrm{t}}_{2}-{\mathrm{t}}_{1}\right)$ between

the time ${\mathrm{t}}_{2}$ when $\frac{2}{3}$ of it has decayed and

the time ${\mathrm{t}}_{1}$ when $\frac{1}{3}$ of it had decayed is

(a) 30 days

(b) 50 days

(c) 60 days

(d) 15 days

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Difficulty Level:

The power obtained in a reactor using ${\mathrm{U}}^{235}$

disintegration is 1000 kW. The mass decay

of ${\mathrm{U}}^{235}$ per hour is

(a)

(b)

(c)

(d)

Concept Questions :-

Mass-energy equivalent
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Difficulty Level:

The half-life of a radioactive isotope X is 50 yr.

It decays to another element Y which is stable.

The two elements X and Y were found to be in

the ratio of 1:15 in a sample of a given rock.

The age of rock was estimated to be

(a) 200 yr

(b) 250 yr

(c) 100 yr

(d) 150 yr

Concept Questions :-

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Difficulty Level:

Fusion reaction takes place at high temperature because

(a) atoms get ionised at high temperature

(b) kinetic energy is high enough to overcome the Coulomb repulsion between nuclei

(c) molecules break up at high temperature

(d) nuclei break up at high temperature

Concept Questions :-

Mass-energy equivalent
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Difficulty Level:

Two radioactive nuclei P and Q, in a given sample decay into a stable nucleus R. At time t=0, the number of P species are $4{N}_{0}$ and that of Q is and that of Q are ${N}_{0}.$Half-life of P(for conversion to R) is 1 min whereas that of Q is 2 min. Initially there are no nuclei of R present in the sample. When number of nuclei of P and Q are equal, the number of nuclei of R present in the sample would be:

(a)$3{N}_{0}$                                          (b)$\frac{9{N}_{0}}{2}$

(c)$\frac{5{N}_{0}}{2}$                                       (d)$2{N}_{0}$

Concept Questions :-

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Difficulty Level:

The mass of a ${}_{3}{}^{7}Li$ nucleus is 0.042u less than the sum of the masses of al  its nucleons.The binding energy per nucleon of ${}_{3}{}^{7}Li$ nucleus is nearly

(a) 46 MeV                              (b) 5.6 MeV

(c) 3.9 MeV                             (d) 23 MeV

Concept Questions :-

Nuclear binding energy
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Difficulty Level:

The activity of a radioactive sample is measured as ${N}_{0}$ counts per minute at t=0 and ${N}_{0}/e$ counts per minute at t=5 min.The time (in minute) at which the activity reduces to half its value is

(a) ${\mathrm{log}}_{e}2/5$                                                         (b)

(c)                                                          (d)

Concept Questions :-

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Difficulty Level:

The decay constant of a radio isotope is $\mathrm{\lambda }.$ If ${\mathrm{A}}_{1}$ and ${\mathrm{A}}_{2}$ are its activities at times ${\mathrm{t}}_{1}$ and ${\mathrm{t}}_{2}$ respectively, the number of nuclei which have decayed during the time $\left({\mathrm{t}}_{1}-{\mathrm{t}}_{2}\right)$

(a) ${\mathrm{A}}_{1}{\mathrm{t}}_{1}-{\mathrm{A}}_{2}{\mathrm{t}}_{2}$                                       (b) ${\mathrm{A}}_{1}-{\mathrm{A}}_{2}$

(c) $\frac{\left({\mathrm{A}}_{1}-{\mathrm{A}}_{2}\right)}{\mathrm{\lambda }}$                                         (d) $\mathrm{\lambda }\left({\mathrm{A}}_{1}-{\mathrm{A}}_{2}\right)$

Concept Questions :-

Types of decay