$\mathrm{Two} \mathrm{nucleons} \mathrm{are} \mathrm{at} \mathrm{a} \mathrm{separation} \mathrm{of} 1 \mathrm{fm}. \mathrm{The} \mathrm{net} \mathrm{force} \mathrm{between} \mathrm{them} \mathrm{is} {\mathrm{F}}_1 \mathrm{if} \mathrm{both} \mathrm{are} \mathrm{neutrons}, {\mathrm{F}}_2 \mathrm{if} \mathrm{both} \mathrm{are} \mathrm{protons} \mathrm{and} {\mathrm{F}}_3 \mathrm{if} \mathrm{one} \mathrm{is}$
$\mathrm{proton} \mathrm{and} \mathrm{other} \mathrm{is} \mathrm{a} \mathrm{neutron}. \mathrm{Hence}$

1.  ${\mathrm{F}}_1 > {\mathrm{F}}_2 > {\mathrm{F}}_3$

2.  ${\mathrm{F}}_2 > {\mathrm{F}}_1 > {\mathrm{F}}_3$

3.  ${\mathrm{F}}_1 = {\mathrm{F}}_3 > {\mathrm{F}}_2$

4.  ${\mathrm{F}}_1 = {\mathrm{F}}_2 > {\mathrm{F}}_3$

The ratio of the radius of the nucleus to the radius of an atom is of the order of :

1.  ${10}^{-5}$

2.  ${10}^{-7}$

3.  ${10}^{-2}$

4.  $10°$

If a radioactive material reduces to 12.5% of its value in 24 days, then its half-life is:

1.  16 days

2.  8 days

3.  4days

4.  2 days

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

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

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

1.  ${}_1{}^1\mathrm{P}$

2.  ${}_1{}^2\mathrm{H}$

3.  ${}_2{}^4\mathrm{He}$

4.  ${}_0{}^1\mathrm{n}$

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

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

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

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