Two samples X and Y contain equal amount of radioactive substance

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 Multiple Choice QuestionsMultiple Choice Questions

41.

A freshly prepared radioactive sample of half-life 4 hours emits radiation of intensity which is 64 times the safe level. The minimum hours after which it would be safe to work with it is

  • 4

  • 6

  • 24

  • 16


42.

A radioactive decay can form an isotope of the original nucleus with the emission of particles

  • one α and four β

  • one α and two β

  • one α and one β

  • four α and one β


43.

A radioactive sample at any instant has its disintegration rate 5000 disintegrations per minute. After 5 min, the rate becomes 1250 disintegration per minute. Then, its decay constant (per minute) is

  • 0.8 loge 2

  • 0.4 loge 2

  • 0.2 loge 2

  • 0.1 loge 2


44.

The distance of closest approach of an α-particle fired towards a nucleus with momentum p, is r. If the momentum of the α-particle is 2p, the corresponding distance of closest approach is

  • r2

  • 2r

  • r4

  • 4r


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45.

If the binding energy per nucleon of deuteron is 1.115 MeV, its mass defect in atomic mass unit is

  • 0.0048

  • 0.0024

  • 0.0012

  • 0.0006


46.

The set which represents the isotope, isobar and isotone respectively is

  • (1H2, 1H3), (79Au197, 80Hg198) and (2He3, 1H2)

  • ( 2He31H1), (79Au197, 80Hg198) and (1H1, 1H3)

  • (2He3, 1H3), (1H2, 1H3) and ( 79Au197, 80Hg198)

  • (1H2, 1H3), (2He3, 1H3) and (79Au197, 80Hg198)


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47.

Two samples X and Y contain equal amount of radioactive substances. If 116th of the sample X and 1256th of the sample Y, remain after 8 h, then the ratio of half periods of X and Y is

  • 2 : 1

  • 1 : 2

  • 1 : 4

  • 1 : 16


A.

2 : 1

For X radioactive substances

      N = N0 12t/Tχ   NN0 = 128/Tχ   116 = 128/TX124 = 128/Tχ    Tχ = 2

For Y radioactive substances,

      NN0 = 128/TY    1256 = 128/TY    128 = 128/TYor     TY = 1   TXTY = 21


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48.

Radioactive Co2760 is transformed into stable Ni2860 by emitting two γ-rays of energies

  • 1.33 MeV and 1.17 MeV in succession

  • 1.17 MeV and 1.33 MeV in succession

  • 1.37 MeV and 1.13 MeV in succession

  • 1.13 MeV and 1.37 MeV in succession


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49.

The activity of a radioactive element decreases to one-third of the original activity A0 in a period of 9 yr. After a further lapes of 9 yr, its activity will be

  • A0

  • 23A0

  • A09

  • A06


50.

Two nucleons are at a separation of 1 fermi. The net force between them is F1 if both are neutrons, F2 if both are protons and F3 if one is proton and the other is a neutron. Then

  • F1 > F2 > F3

  • F1 = F3 > F2

  • F2 > F1 > F3

  • F1 = F2 > F3


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