The initial activity of a certain radioactive isotope was measured as 16000 counts per minute. That the only activity measured was due to this and that its activity after 12 hours was 2000 counts/minute. Its half-life, in hours, is nearest to-

1.  9.0

2.  6.0

3.  4.0

4.  3.0

How much energy is contained in a particle that has a mass of $1 \mu g?$

$1. 9\times {10}^7 J$
$2. 9\times {10}^{16} J$
$3. 9\times {10}^5 J$
$4. 9\times {10}^{11} J$

A radioactivity nuclide can  decay simultaneously by two different processes that have decay constants ${\mathrm{\lambda }}_1$ and ${\mathrm{\lambda }}_2$ . The effective decay constant of the nuclide is $\mathrm{\lambda }.$ Then-

1.  $\mathrm{\lambda } = {\mathrm{\lambda }}_1 + {\mathrm{\lambda }}_2$

2.  $\mathrm{\lambda } = \frac{1}{2}\left({\mathrm{\lambda }}_1 + {\mathrm{\lambda }}_2\right)$

3.  $\frac{1}{\mathrm{\lambda }} = \frac{1}{{\mathrm{\lambda }}_1} + \frac{1}{{\mathrm{\lambda }}_2}$

4.  $\mathrm{\lambda } = \sqrt{{\mathrm{\lambda }}_1{\mathrm{v}}_2}$

The binding energy per nucleon in deuterium and helium nuclei are $1.1 \mathrm{MeV}$ and $7.0 \mathrm{MeV},$ respectively. When two deuterium nuclei fuse to form a helium nucleus, the energy released in the fusion is

1.  47.12 MeV

2.  34.4 MeV

3.  11.8 MeV

4.  23.6 MeV

A chain reaction is continuous due to

1.  Large mass defect

2.  Large energy

3.  Production of more neutrons in fission

4.  None of these

Which of the following is deflected by electric field 

(1) X-rays

(2) Gamma rays

(3) Neutrons

(4) α-particles

The half-life of a radioactivity isotope X is 100years. It decays to an element Y which is stable. The two elements are found to be ratio 1: 32 in a sample of a given rock. Assuming that at the time of formation of the rock there was only isotope X, then estimate the age of the rock.

1.  300 years

2.  400 years

3.  500 years

4.  600 years

$\mathrm{In} \mathrm{the} \mathrm{equation} {}_{13}{}^{27}\mathrm{AI} + {}_2{}^4\mathrm{He} \to {}_{15}{}^{30}\mathrm{P} + \mathrm{X} \mathrm{where} \mathrm{X} \mathrm{is}-$

1.  ${}_1{}^1\mathrm{P}$

2.  ${}_1{}^2\mathrm{H}$

3.  ${}_2{}^4\mathrm{He}$

4.  ${}_0{}^1\mathrm{n}$

Binding energy per nucleon is:

1.  Maximum for middle-order elements

2.  Maximum for lighter order elements

3.  Maximum for heavier order elements

4.  None of these

The half-life of a radioactive material depends on

1.  The initial amount of material

2.  Rate of disintegration

3.  Decay constant

4.  Temperature and pressure