In a radioactive substance at t = 0, the number of atoms is 8, its half-life period is 3 yr. The number of atoms equal to will remain after an interval of:
1. 9 yr
2. 8 yr
3. 6 yr
4. 24 yr
What is the respective number of and -particles emitted in the following radioactive decay?
1. 6 and 8
3. 6 and 6
3. 8 and 8
4. 8 and 6
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
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 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 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.
2.
3.
4.
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.
2.
3.
4.
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. |