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

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 Multiple Choice QuestionsMultiple Choice Questions

221.

S32 absorbs energy and decays into which element after two α-emissions?

  • Carbon

  • Aluminium

  • Oxygen

  • magnesium


222.

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

  • Water

  • Heavy water

  • Cadmium

  • Graphite


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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.


A.

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

Multiplication factor (k) is a measure of the growth rate of neutrons in the reactor. For k = 1;   the operation of the reaction is said to be critical condition at which sustained chain reaction occurs. If k becomes greater than the reaction rate and reactor power increases exponentially.


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224.

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.


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225.

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.


226.

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.


227.

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

  • 12λ

  • 14λ


228.

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


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229.

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

  • mp/me

  • mp2 / me2

  • 1

  • memp


230.

A nucleus of mass number 220 decays by α decay. The energy released in the reaction is 5 MeV. The kinetic energy of an α-particle is

  • 154MeV

  • 2711 MeV

  • 5411 MeV

  • 5554 MeV


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