In a radioactive substance at t = 0, the number of atoms is 8$×{10}^{4}$, its half-life period is 3 yr. the number of atoms $1×{10}^{4}$ will remain after interval [UP CPMT 2010]

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

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What is the respective number of $\alpha$ and $\beta$-particles emitted in the following radioactive decay?

(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 :-

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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 ${}_{2}H{e}^{4}$ is (mass of helium nucleus = 4.0015 u)

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

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

(1) ${E}_{a}-3{E}_{b}=Q$                    (2) $3{E}_{b}-{E}_{a}=Q$

(3) ${E}_{a}+3{E}_{b}=Q$                    (4) ${E}_{b}+3{E}_{a}=Q$

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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

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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) $\frac{1}{{e}^{n}}$            (2) ${e}^{n}$            (3) $1-\frac{1}{{e}^{n}}$            (4) ${\left(\frac{1}{e-1}\right)}^{n}$

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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

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The energy equivalent of one atomic mass unit is 

(1)                    (2)

(3) 931 MeV                             (4) 9.31 MeV

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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