S³² absorbs energy and decays into which element after two $\mathrm{\alpha }$-emissions?

• Carbon

• Aluminium

• Oxygen

• magnesium

Among the following which is used to control the rate of reaction of nuclear fissions reactions?

• Water

• Heavy water

• Cadmium

• Graphite

223.

Assertion:  For nuclear reactor, it is desirable to have k = 1.

Reason: Sustained chain reaction occur at this critical condition.

• 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.

Assertion: Mass defect in nuclear reactions is less than 1%.

Reason: In nuclear reaction change in BE/N is generally less than 1%.

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

• If both assertion 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 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