The radioactivity of an element becomes $\frac{1}{64}th$ of its original value in 60 seconds. Then the half value period is

(1) 5 sec              (2) 10 sec            (3) 20 sec            (4) 30 sec

A and B are two radioactive substances whose half-lives are 1 and 2 years respectively. Initially 10 g of A and 1 g of B is taken. The time (approximate) after which they will have the same quantity remaining is

(1) 6.62 yr                (2) 5 yr                (3) 3.2 yr                   (4) 7 yr

Complete the equation for the following fission process-

$U_{92}^{235}+n_0^1\to S{r}_{38}^{90}+........$  

(1) $X{e}_{{}_{54}}^{143}+3<mspace\; width="1em"></mspace>n_0^1$                      (2) $X{e_{{}_{54}}^{145}}^{}$

(3) $X{e_{{}_{57}}^{142}}^{}$                                   (4) $X{e_{{}_{54}}^{142}}^{}+n_0^1$

A nucleus ruptures into two nuclear parts, which have their velocity ratio equal to 2:1. what will be the ratio of their nuclear size (nuclear radius) ? [1996]

(1) $2^{1/3}<mspace\; width="1em"></mspace>:<mspace\; width="1em"></mspace>1$              (2) $1<mspace\; width="1em"></mspace>:<mspace\; width="1em"></mspace>2^{1/3}$             (3) $3^{1/2}<mspace\; width="1em"></mspace>:<mspace\; width="1em"></mspace>1$                (4) $1<mspace\; width="1em"></mspace>:<mspace\; width="1em"></mspace>3^{1/2}$

Half-life of a radioactive substance is 20 min. Difference between points of time when it is 33% disintegrated and 67% disintegrated is approximately-

(1) 10 min            (2) 20 min            (3) 30 min            (4) 40  min

The binding energy per nucleon is maximum in case of 

1. ${}_{2}H{e}^4$                                         

2. ${}_{26}F{e}^{56}$

3. ${}_{56}B{a}^{141}$                                     

4. ${}_{92}U_{235}$

In nuclear fission process, energy is released because [2001]

(1) mass of products is more than mass of nucleus.

(2) total binding energy of products formed due to nuclear fission is more than that the parent fissionable material.

(3) total binding energy of products formed due to nuclear fission is less than parent fissionable material.

(4) mass of some particles is converted into energy.

The mass number of helium is 4 and that for suphur is 32. The radius of sulphur nuclei is larger than that of helium by

1.  $\sqrt{8}$

2.  4

3.  2

4.  8

A freshly prepared radioactive source of half-life 2 hrs. emits radiations of intensity which is 64 times the permissible safe level. The minimum time after which it would be possible to work safely with the source is

1.  6 hrs.

2.  12 hrs.

3.  24 hrs.

4.  128 hrs.  

$\mathrm{If}<mspace\; width="1em"></mspace>\mathrm{the}<mspace\; width="1em"></mspace>\mathrm{binding}<mspace\; width="1em"></mspace>\mathrm{energy}<mspace\; width="1em"></mspace>\mathrm{per}<mspace\; width="1em"></mspace>\mathrm{nucleon}<mspace\; width="1em"></mspace>\mathrm{in}<mspace\; width="1em"></mspace>{}_3\mathrm{Li}_7<mspace\; width="1em"></mspace>\mathrm{and}<mspace\; width="1em"></mspace>{}_2\mathrm{He}_4<mspace\; width="1em"></mspace>\mathrm{nuclei}<mspace\; width="1em"></mspace>\mathrm{are}<mspace\; width="1em"></mspace>\mathrm{respectively}<mspace\; width="1em"></mspace>5.60<mspace\; width="1em"></mspace>\mathrm{MeV}<mspace\; width="1em"></mspace>\mathrm{and}$
$7.06<mspace\; width="1em"></mspace>\mathrm{MeV},<mspace\; width="1em"></mspace>\mathrm{then}<mspace\; width="1em"></mspace>\mathrm{the}<mspace\; width="1em"></mspace>\mathrm{energy}<mspace\; width="1em"></mspace>\mathrm{of}<mspace\; width="1em"></mspace>\mathrm{proton}<mspace\; width="1em"></mspace>\mathrm{in}<mspace\; width="1em"></mspace>\mathrm{the}<mspace\; width="1em"></mspace>\mathrm{reaction}<mspace\; width="1em"></mspace>{}_2\mathrm{Li}_7<mspace\; width="1em"></mspace>+<mspace\; width="1em"></mspace>\mathrm{p}<mspace\; width="1em"></mspace>\to 2_2{\mathrm{He}}^4<mspace\; width="1em"></mspace>\mathrm{is}<mspace\; width="1em"></mspace>:$

1.  19.6 MeV

2.  2.4 MeV

3.  8.4 MeV

4.  17.3 MeV