Mean life of a radioactive sample is 100 seconds. Then its half-l

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 Multiple Choice QuestionsMultiple Choice Questions

71.

The nuclear reactor at Kaiga is a

  • research reactor 

  • fusion reactor

  • breeder reactor 

  • power reactor


72.

A count rate meter shows a count of 240 per minute from a given radioactive source. One hour later the meter shows a count rate of 30 per minute. The half-life of the source is

  • 80 min

  • 120 min

  • 20 min

  • 30 min


73.

Two nucleons are at a separation of one Fermi. Protons have a charge of +16 x 10-19 C. The net nuclear force between them is F1, if both are neutrons, F2 if both are protons and F3 if one is proton and the other is neutron. Then

  • F1 = F2 > F3

  • F1 = F2 = F3

  • F1 < F2 < F3

  • F1 > F2 > F3


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74.

Mean life of a radioactive sample is 100 seconds. Then its half-life (in minutes) is

  • 0.693

  • 1

  • 10-4

  • 1.155


D.

1.155

Half life T/2 = T1.44 = 1001.44 sec                    = 69.44 sec = 69.4460                     1.155 min


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75.

Consider two nuclei of the same radioactive nuclide. One of the nuclei was created in a supernova explosion 5 billion years ago. The other was created in a nuclear reactor 5 minutes ago. The probability of decay during the next time is

  • different for each nuclei

  • nuclei created in explosion decays first

  • nuclei created in the reactor decays first

  • independent of the time of creation


76.

Activity of a radioactive sample decreases to (1/3)rd of its original value in 3 days. Then,in 9 days its activity will become 

  • (1/27) of the original value

  • (1/9) of the original value

  • (1/18) of the original value

  • (1/3) of the original value


77.

If r1 and r2 are the radii of the atomic nuclei of mass numbers 64 and 125 respectively, then the ratio (r1/r2) is

  • 64125

  • 64125

  • 54

  • 45


78.

The ionisation energy of Li2+ is equal to

  • 9hcR

  • 6hcR

  • 2hcR

  • hcR


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79.

A radioactive element forms its own isotope after 3 consecutive disintegrations. The particles emitted are

  • 3β-particles

  • 2β-particles and 1α-particle

  • 2β-particles and 1γ-particle

  • 2α-particles and 1β-particle


80.

A radioactive substance contains 10000 nuclei and its half-life period is 20 days. The number of nuclei present at the end of 10 days is

  • 7070

  • 9000

  • 8000

  • 7500


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