In a radioactive substance at t = 0, the number of atoms is 8×104, its half-life period is 3 yr. the number of atoms 1×104 will remain after interval [UP CPMT 2010]

(1) 9 yr              (2) 8 yr              (3) 6 yr             (4) 24 yr

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Radioactivity
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What is the respective number of α and β-particles emitted in the following radioactive decay?

X90200Y80168   

(1) 6 and 8               (2) 6 and 6           (3) 8 and 8          (4) 8 and 6   

Concept Questions :-

Types of decay
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The half-life of radium is 1622 years. How long will it take for seven-eighth of a given amount of radium to decay

(1) 3244 years             (2) 6488 years           (3) 4866 years        (4) 811 years

Concept Questions :-

Radioactivity
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The mass of a proton is 1.0073 u and that of the neutron is 1.0087 u (u = atomic mass unit) The binding energy of H2e4 is (mass of helium nucleus = 4.0015 u)

(1) 28.4 MeV          (2) 0.061 u             (3) 0.0305 J          (4) 0.0305 erg

Concept Questions :-

Mass-energy equivalent
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The binding energies of the nuclei A and B are Ea and Eb respectively. Three atoms of the element B fuse to give one atom of element A and an energy Q is released.Then Ea, Eb and Q are related as

(1) Ea-3Eb=Q                    (2) 3Eb-Ea=Q

(3) Ea+3Eb=Q                    (4) Eb+3Ea=Q

Concept Questions :-

Nuclear binding energy
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A free neutron decays into a proton, an electron and 

(1) a beta particle                 (2) an alpha particle

(3) an antineutrino                (4) a neutrino

Concept Questions :-

Types of decay
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In a radioactive sample the fraction of initial number of radioactive nuclei, which remains undecayed after n mean lives is 

(1) 1en            (2) en            (3) 1-1en            (4) 1e-1n

Concept Questions :-

Radioactivity
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The activity of a radioactive sample is measured as 9750 counts/min at t = 0 and as 975 counts/min at t = 5 min. The decay constant is approximately:

(1) 0.922/min           

(2) 0.691/min         

 (3) 0.461/min           

(4) 0.230/min

Concept Questions :-

Radioactivity
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The energy equivalent of one atomic mass unit is [1992]

(1) 1.6×10-19 J                   (2) 6.02×1023 J

(3) 931 MeV                             (4) 9.31 MeV

Concept Questions :-

Mass-energy equivalent
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Solar energy is due to

1. fusion reaction

2. fission reaction

3. combustion reaction

4. chemical reaction

Concept Questions :-

Mass-energy equivalent
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