Select Chapter Topics:
Q. No.From a newly formed radioactive substance (Half-life 2 hours), the intensity of radiation is 64 times the permissible safe level. The minimum time after which work can be done safely from this source is:
1. 6 hours
2. 12 hours
3. 24 hours
4. 128 hours
1. 6 hours
2. 12 hours
3. 24 hours
4. 128 hours
81%
Level 1: 80%+
Hints
The half-life of a radioactive substance is 20 minutes. The time between 20% and 80% decay will be:
1. 20 minutes
2. 40 minutes
3. 30 minutes
4. 25 minutes
76%
Level 2: 60%+
Hints
During negative -decay:
| 1. | a neutron converts into proton. |
| 2. | a proton converts into neutron. |
| 3. | neutron to proton ratio increases. |
| 4. | None of these |
Subtopic: Types of Decay |
76%
Level 2: 60%+
Hints
An atomic nucleus \({}_{90}^{232}\mathrm{Th}\) emits several \(\alpha\) and \(\beta\) radiations and finally reduces to \({}_{82}^{208}\mathrm{Pb}.\) It must have emitted:
1. \(4\alpha~\text{and}~2\beta\)
2. \(6\alpha~\text{and}~4\beta\)
3. \(8\alpha~\text{and}~24\beta\)
4. \(4\alpha~\text{and}~16\beta\)
1. \(4\alpha~\text{and}~2\beta\)
2. \(6\alpha~\text{and}~4\beta\)
3. \(8\alpha~\text{and}~24\beta\)
4. \(4\alpha~\text{and}~16\beta\)
Subtopic: Types of Decay |
85%
Level 1: 80%+
Hints
\({}_{10}^{22}\mathrm{Ne}\) nucleus after absorbing energy decays into two \(\alpha \text{-particle}\) and an unknown nucleus. The unknown nucleus is:
1. Nitrogen
2. Carbon
3. Boron
4. Oxygen
1. Nitrogen
2. Carbon
3. Boron
4. Oxygen
Subtopic: Types of Decay |
70%
Level 2: 60%+
Hints
Fission of nuclei is possible because the binding energy per nucleon in them:
| 1. | increases with mass number at high mass numbers. |
| 2. | decreases with mass number at high mass numbers. |
| 3. | increases with mass number at low mass numbers. |
| 4. | decreases with mass number at low mass numbers. |
Subtopic: Nuclear Binding Energy |
62%
Level 2: 60%+
Hints
If an electron and a positron annihilate, then the energy released is:
1. \(3.2\times 10^{-13}~\text{J}\)
2. \(1.6\times 10^{-13}~\text{J}\)
3. \(4.8\times 10^{-13}~\text{J}\)
4. \(6.4\times 10^{-13}~\text{J}\)
1. \(3.2\times 10^{-13}~\text{J}\)
2. \(1.6\times 10^{-13}~\text{J}\)
3. \(4.8\times 10^{-13}~\text{J}\)
4. \(6.4\times 10^{-13}~\text{J}\)
Subtopic: Mass-Energy Equivalent |
65%
Level 2: 60%+
Hints
In nuclear reaction \({}_{2}^{4}\mathrm{He}+ {}_{Z}^{A}\mathrm{X}\rightarrow {}_{Z+2}^{A+3}\mathrm{X}+\mathrm{B},\) \(\mathrm {B}\) denotes:
| 1. | electron | 2. | positron |
| 3. | proton | 4. | neutron |
Subtopic: Types of Decay |
66%
Level 2: 60%+
Hints
The mass of an -particle is:
| 1. | less than the sum of masses of two protons and two neutrons. |
| 2. | equal to the mass of four protons. |
| 3. | equal to the mass of four neutrons. |
| 4. | equal to the sum of masses of two protons and two neutrons. |
Subtopic: Nuclear Binding Energy |
58%
Level 3: 35%-60%
Hints
Subtopic: Mass-Energy Equivalent |
Level 3: 35%-60%
Hints
Select Chapter Topics:
© 2026 GoodEd Technologies Pvt. Ltd.