A nucleus XZA has mass represented by m (A,Z). If mp an

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 Multiple Choice QuestionsMultiple Choice Questions

161.

Radioactive decay will occur as follows

Rn86220      PO84216 + He24 Half life = 55sPO84216      Pb82212  + He24 Half life = 0.66 sPb82812    BL82212 + λ°e Half life = 10.6 h

If a certain mass of radon (Rn = 220) is allowed to decay in a certain container; then after 5 minutes the element with the greater mass will be

  • radon

  • polonium

  • lead

  • bismuth


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162.

A nucleus XZA has mass represented by m (A,Z). If mp and mn denote the mass of proton and neutron respectively and BE the binding energy (in MeV) then.

  • BE = [m(A,Z) - Zmp - (A-Z)mn]C2

  • BE = [Zmp + (A -Z)mn - m(A,Z)]c2

  • BE = [Zmp + Amn - m (A,Z)]c2

  • BE = m (A,Z) - Zmp - (A-Z) mN


B.

BE = [Zmp + (A -Z)mn - m(A,Z)]c2

In the case of the formation of the nucleus, the evolution of energy equals the binding energy of the nucleus takes place due to the disappearance of a fraction of total mass. If the quantity of mass disappearing is Δm, then the binding energy is

BE = Δmc2

From the above points, it is clear that the mass of the nucleus must be less than the sum of the masses of the constituent neutrons and protons. Thus, 

Δm = Zmp - Nmn - m(A,Z)

Where m (A, Z) is the mass of the atom of mass number A atomic number Z. Hence, the binding energy of a nucleus is

BE = [Zmp + Nmn - m(A,Z)]c2

BE = [Zmp + (A-Z) mn - m(A,Z)] c2


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163.

The half-life period of a radioactive element X is the same as the mean life of another radioactive element Y. Initially, both of them have the same numbers of atoms then,

  • X and Y have the same decay rate initially

  • X and Y decay at the same rate always

  • Y will decay at a faster rate than X

  • X will decay at a faster rate than Y


164.

The mass of a proton is 1847 times that of an electron. An electron and a proton are injected into a uniform electric field at right angle to the direction of the field with the same initial K.E.

  • The electron trajectory will be less curved than the proton trajectory.

  • both the trajectories will be straight

  • the proton trajectory will be less curved than the electron trajectory.

  • both the trajectories will be equally curved.


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165.

If the energy released in the fission of one nucleus is 3.2x10-11J, then number of nuclei required per second in a power plant of 16 kW is

  • 0.5×1014

  • 0.5×1012

  • 5×1012

  • 5×1014


166.

If an electron has orbital angular momentum quantum number l =7 then it will have an orbital angular momentum equal to 

  • 56h2π

  • 57h2π

  • 42h2π

  • 7h2π


167.

The half-life of a radioactive substance is 3.6 days. How much of 20 mg of this radioactive substance will remain after 36 days?

  • 0.0019 mg

  • 1.019 mg

  • 1.109 mg

  • 0.019 mg


168.

In the reaction given below A22286  B21084. How many α and β particles are emitted?

 

  • 6α, 3β

  • 3α, 4β

  • 4α, 3β

  • 3α,6β


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169.

The phenomenon of radioactivity is :

  • exothermic change which increases or decreases with  temperature

  • increases on applied pressure

  • nuclear process does not depend on external factors

  • none of the above


170.

In the reaction,H12 +H13  He24 + n01 if the binding energies of H12,   13H  and   He24 are respectively a, b and c (in MeV), then the energy in this reaction is released in this reaction is

  • c + a - b

  • c - a - b

  • a + b + c

  • a +b - c


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