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11.

The half - life of a radioactive isotope X is 50 yr. It decays to another element Y which is stable. The two elements X and Y were found to be in the ratio of 1: 15 in a sample of a given rock. The age of the rock was estimated to be

  • 200 yr

  • 250 yr

  • 100 yr

  • 100 yr

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12.

Fusion reaction takes place at high temperature because

  • atoms get ionised at high temperature

  • kinetic energy is high enough to overcome the coulomb repulsion between nuclei

  • molecules break up at high temperature

  • molecules break up at high temperature

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13.

A nucleus X presubscript straight n presuperscript straight m emits one α - particle and two β- particles. The resulting nucleus is 

  • straight Z presubscript straight n presuperscript straight m minus 6 end presuperscript
  • straight X presubscript straight n presuperscript straight m minus 4 end presuperscript space space
  • straight Y presubscript straight n minus 2 end presubscript presuperscript straight m minus 4 end presuperscript
  • straight Y presubscript straight n minus 2 end presubscript presuperscript straight m minus 4 end presuperscript
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14.

A nucleus of uranium decays at rest into nuclei of thorium and helium. Then, 

  • the helium nucleus has more kinetic energy than the thorium nucleus

  • the helium nucleus has less momentum than the thorium nucleus

  • the helium nucleus has more momentum than the thorium nucleus

  • the helium nucleus has more momentum than the thorium nucleus

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15.

Two radioactive nuclei P and Q, in a given sample decay into a stable nucleous R. At time t =0, number of P species are 4No and that of Q are No.Half -life of P (for conversion to R) is 1 min where asthat of Q is 12 min. Initially there are no nuclei of R present in the sample. When number of nuclei of R presnent in the sample would be


  • 3No

  • 9No / 2

  • 5No/2

  • 5No/2

1298 Views

16.

The mass of a Li presubscript 3 presuperscript 7 nucleus is 0.042u less than the sum of the masses of all its nucleons. The binding energy per nucleon is Li presubscript 3 presuperscript 7 nucleus is nearly

  • 46 MeV

  • 5.6 MeV

  • 3.9 MeV

  • 3.9 MeV

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17.

The activity of a radioactive sample is measured as No counts per minute at t = 0 and No/e counts per minute at t = 5 min. The time (in minute) at which the activity reduces to half its value is

  • loge 2 /5

  • 5/ loge 2

  • 5 log10 2

  • 5 log10 2

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18.

The decay constant of a ratio isotope is λ. If A1 and A2 are its activities at times t1 and t2 respectively, te number of nuclei which have decayed during the time (t1-t2)

  • A1t1 - A2t2

  • A1 - A2

  • (A1 - A2)/λ

  • (A1 - A2)/λ

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19.

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

  • 23.6 MeV

  • 2.2 MeV

  • 28.0 MeV

  • 28.0 MeV

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20.

In the nuclear decay given below,

straight X presubscript straight Z presuperscript straight A space rightwards arrow straight Y presubscript straight Z plus 1 end presubscript presuperscript straight A space rightwards arrow space straight B presubscript straight Z minus 1 end presubscript presuperscript straight A minus 4 end presuperscript asterisk times space rightwards arrow space straight B presubscript straight Z minus 1 end presubscript presuperscript straight A minus 4 end presuperscript
the particle emitted in the sequence are

  • β, α, γ

  • γ, β, α, 

  •  β,γ, α

  •  β,γ, α

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