A nuclide A undergoes `alpha` - decay and another nuclide B undergoes `beta`-decay
(a) All the `alpha`-particle emitted by A will have almost the same speed
( b) The `alpha`- particle emitted by A may have widely different speeds
(c) All the `beta`-particle emitted by B will have almost the same speed
(d) The `beta`-particle emitted by B may have widely different speeds

Options

A. a, b are true
B. b, c are true
C. b, d are true
D. a, d are true

Answer

To solve the question regarding the behavior of alpha and beta particles emitted during nuclear decay, we will analyze each statement step by step.

### Step-by-Step Solution:

1. **Understanding Alpha Decay**:
- In alpha decay, a nuclide A emits an alpha particle (which consists of 2 protons and 2 neutrons) and transforms into a daughter nuclide.
- The energy released during this process is quantized, meaning that all emitted alpha particles have the same kinetic energy.

2. **Analyzing Statement (a)**:
- "All the alpha particles emitted by A will have almost the same speed."
- Since all alpha particles have the same kinetic energy, they will also have almost the same speed.
- **Conclusion**: This statement is **True**.

3. **Analyzing Statement (b)**:
- "The alpha particle emitted by A may have widely different speeds."
- This contradicts the previous conclusion because we established that all alpha particles have the same speed due to their identical kinetic energy.
- **Conclusion**: This statement is **False**.

4. **Understanding Beta Decay**:
- In beta decay, a nuclide B emits a beta particle (an electron or positron) and transforms into a different daughter nuclide.
- The energy spectrum of beta particles is continuous, meaning that they can have a range of kinetic energies and speeds.

5. **Analyzing Statement (c)**:
- "All the beta particles emitted by B will have almost the same speed."
- Since the beta particles have a continuous energy spectrum, they will not have the same speed.
- **Conclusion**: This statement is **False**.

6. **Analyzing Statement (d)**:
- "The beta particle emitted by B may have widely different speeds."
- Given that beta particles can have a range of energies, this statement is consistent with the continuous spectrum of beta decay.
- **Conclusion**: This statement is **True**.

### Final Conclusion:
The true statements are (a) and (d). Therefore, the correct answer is that statements A and D are true.