Assertion:  It is very easy to detect neutrino in nature. 

Reason:  It has high affinity to interact with matter.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both asertion and reason are true and reason is not correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion:  It is desirable to slow down fast moving neutrons to sustain controlled chain reactions. 

Reason:  Slow moving neutrons efficiently collides with  U²³⁵.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If assertion and reason are false.

Two radioactive substances A and 8 have decay constants 5A and A respectively. At I =0, they have the same number of nuclei. The ratio of number of nuclei of A to those of 8 will be (1/e² ) after a time

• 4λ

• 2λ

• $\frac{1}{2\mathrm{\lambda }}$

• $\frac{1}{4\mathrm{\lambda }}$

The intensity of gamma radiation from a given source is  I.  On passing through 36 mm of lead, it is reduced to l/8. The thickness of lead which will reduce the intensity to l/2  will be

• 18 mm

• 12 mm

• 6 mm

• 9 mm

What is the ratio of Bohr magnetron to the nuclear magnetron?

• m_p/m_e

• ${\mathrm{m}}_{\mathrm{p}}^2 / {\mathrm{m}}_{\mathrm{e}}^2$

• 1

• $\frac{{\mathrm{m}}_{\mathrm{e}}}{{\mathrm{m}}_{\mathrm{p}}}$

A nucleus of mass number 220 decays by $\mathrm{\alpha }$ decay. The energy released in the reaction is 5 MeV. The kinetic energy of an $\mathrm{\alpha }$-particle is

• $\frac{1}{54}$MeV

• $\frac{27}{11}$ MeV

• $\frac{54}{11}$ MeV

• $\frac{55}{54}$ MeV

107.

If  the  half  lives  of  a  radioactive  element  for  $\mathrm{\alpha }$  and  β  decay  are  4  years  and  12  years  respectively,  the  ratio  of  its  initial  activity  and  that  after  12  years will be

• 6.25 %

• 12.5 %

• 25 %

• 50 %

A radioactive nucleus is being produced  at  a constant  rate  $\mathrm{\alpha }$  per  second. Its  decay  constant  is  λ. If N₀ are the  number  of  nuclei  at  time  t = 0, then the maximum number of  nuclei possible are

• N₀  +  $\frac{\mathrm{\alpha }}{\mathrm{\lambda }}$

• N₀

• $\frac{\mathrm{\lambda }}{\mathrm{\alpha }}$ + N₀

• $\frac{\mathrm{\alpha }}{\mathrm{\lambda }}$

Assertion: Nuclei  having mass  number  about  60 are  most stable. 

Reason:  When  two  or  more  light  nuclei  are  combined  into  a  heavier  nucleus, then the binding  energy  per  nucleon  will increase.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

N₁ atoms of a radioactive element emit N₂ beta particles per second. The decay constant of the element is ( m s^-1 )

• N₁/N₂

• N₂/N₁

• N₁ ( ln2 )

• N₂ ( ln2 )