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
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.
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.
2.
3.
4.
The half-life period of a radioactive substance is 6 h. If after 24 h, activity is 0.01 Ci, what was the initial activity?
1. 0.04 Ci
2. 0.08 Ci
3. 0.24 Ci
4. 0.16 Ci
Which of the following is used as a moderator in nuclear reactors?
1. Plutonium
2. Cadmium
3. Heavy water
4. Uranium