Assertion Ionisation power of `alpha`-particles is maximum while penetration power of `gamma`-rays is maximum.
Reason `alpha`-particles are haaviest particles, while `gamma`-rays have maximum energy.

Options

A. If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
B. If both Assertion and Reason are true but Reason are true but Reason is not correct explanation of Assertion.
C. If Assertion is true but Reason is false.
D. If Assertion is false but Reason is true.

Answer

To analyze the given assertion and reason, we will break down the concepts of ionization power and penetration power of alpha particles and gamma rays.

### Step 1: Understanding Ionization Power
- **Ionization Power** refers to the ability of a particle to ionize atoms as it passes through matter.
- Alpha particles are positively charged and relatively heavy (they are helium nuclei). Due to their mass and charge, they can cause significant ionization as they interact with matter, leading to a high ionization power.

**Hint:** Remember that the charge and mass of a particle influence its ability to ionize atoms.

### Step 2: Understanding Penetration Power
- **Penetration Power** is the ability of a particle to pass through matter without being absorbed or deflected.
- Gamma rays are electromagnetic radiation with no mass and no charge. They have very high energy and can penetrate materials much more effectively than charged particles like alpha particles. This gives gamma rays maximum penetration power.

**Hint:** Consider how mass and charge affect the ability of particles to penetrate materials.

### Step 3: Analyzing the Assertion
- The assertion states that the ionization power of alpha particles is maximum. This is true because their heavy mass and positive charge allow them to ionize many atoms as they pass through matter.

**Hint:** Think about how the properties of alpha particles contribute to their ionization ability.

### Step 4: Analyzing the Reason
- The reason provided states that alpha particles are the heaviest particles and gamma rays have maximum energy. This is also true. The heaviness of alpha particles contributes to their high ionization power, while the high energy of gamma rays contributes to their maximum penetration power.

**Hint:** Relate the properties of particles (mass and energy) to their respective behaviors in matter.

### Step 5: Conclusion
- Both the assertion and the reason are correct. The reason correctly explains why the assertion is true: the heaviness of alpha particles leads to maximum ionization power, while the high energy of gamma rays leads to maximum penetration power.

**Final Answer:** Both assertion and reason are correct, and the reason is the correct explanation for the assertion.