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 H2e42He4 is (mass of helium nucleus = 4.0015 u)
1. 28.4 MeV
2. 0.061 u
3. 0.0305 J
4. 0.0305 erg
The binding energies of the nuclei A and B are Ea and EbEa 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, EbEa, Eb and Q are related as:
1. Ea-3Eb=QEa−3Eb=Q
2. 3Eb-Ea=Q3Eb−Ea=Q
3. Ea+3Eb=QEa+3Eb=Q
4. Eb+3Ea=QEb+3Ea=Q
A free neutron decays into a proton, an electron and:
1. A beta particle.
2. An alpha particle.
3. An antineutrino.
4. A neutrino.
In a radioactive sample the fraction of initial number of radioactive nuclei, which remains undecayed after n mean lives is:
1. 1en1en
2. enen
3. 1-1en1−1en
4. (1e-1)n(1e−1)n
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
Solar energy is due to:
1. | fusion reaction. | 2. | fission reaction. |
3. | combustion reaction. | 4. | chemical reaction. |
At time t = 0, N1 nuclei of decay constant λ1 and N2 nuclei of decay constant λ2 are mixed. The decay rate of the mixture is:
1. -N1N2e-(λ1+λ2)t−N1N2e−(λ1+λ2)t
2. -(N1N2)−(N1N2) e-(λ1+λ2)te−(λ1+λ2)t
3. -(N1λ1e-λ1t)−(N1λ1e−λ1t) ++ N2λ2e-λ2tN2λ2e−λ2t
4. -N1λ1N2λ2e-(λ1+λ2)t−N1λ1N2λ2e−(λ1+λ2)t
A nucleus XmnmnX emits one αα and two β-β−particles. The resulting nucleus is
1. Xm-4nm−4nX
2. Xm-4n-2m−4n−2X
3. Xm-4n-4m−4n−4X
4. None of these
The half-life period of a radioactive substance is 6 h. If after 24 h, activity is 0.01 μμCi, what was the initial activity?
1. 0.04 μμCi
2. 0.08 μμCi
3. 0.24 μμCi
4. 0.16 μμCi