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

Subtopic:  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

3. 6 and 6

3. 8 and 8

4. 8 and 6   

Subtopic:  Radioactivity | 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

Subtopic:  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

Subtopic:  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

Subtopic:  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

Subtopic:  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

Subtopic:  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

Subtopic:  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

Subtopic:  Mass-energy equivalent |
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Solar energy is due to

1. fusion reaction

2. fission reaction

3. combustion reaction

4. chemical reaction

Subtopic:  Mass-energy equivalent |
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