Assertion : A person wil hear no sound if he is moving away from the source of sound with the speed of sound.
Reason : Because the relative velocity of the sound waves with respect to the person is infinite.

Options

A. If both assertion and reason are correct and reason is a correct explanation of the assertion.
B. If both assertion and reason are correct but reason is not the correct explanation of assertion.
C. If assertion is correct but reason is incorrect
D. If assertion is incorrect but reason is correct.

Answer

To solve the question, we need to analyze the assertion and the reason provided.

### Step 1: Understand the Assertion
The assertion states that a person will hear no sound if he is moving away from the source of sound with the speed of sound.

### Step 2: Analyze the Situation
Let’s denote:
- Speed of sound = \( v \)
- Speed of the person = \( v_0 = v \) (since the person is moving away with the speed of sound)

### Step 3: Apply the Doppler Effect Formula
The formula for the apparent frequency \( f' \) heard by the observer (the person) when moving away from a stationary source is given by:
\[ f' = f_0 \cdot \frac{v - v_0}{v - v_s} \]
Where:
- \( f_0 \) = original frequency of the sound
- \( v \) = speed of sound
- \( v_0 \) = speed of the observer (person)
- \( v_s \) = speed of the source (which is 0 since the source is stationary)

### Step 4: Substitute the Values
Since the person is moving away from the source at the speed of sound:
\[ f' = f_0 \cdot \frac{v - v}{v - 0} \]
This simplifies to:
\[ f' = f_0 \cdot \frac{0}{v} = 0 \]

### Step 5: Conclusion from the Assertion
Since the apparent frequency \( f' = 0 \), the person hears no sound. Thus, the assertion is correct.

### Step 6: Analyze the Reason
The reason states that the relative velocity of the sound waves with respect to the person is infinite.

### Step 7: Evaluate the Relative Velocity
The relative velocity \( v_{relative} \) between the sound and the person is given by:
\[ v_{relative} = v - v_0 = v - v = 0 \]
This means there is no relative motion between the sound waves and the person. Therefore, the reason is incorrect.

### Final Conclusion
- The assertion is correct: A person will hear no sound if he is moving away from the source of sound with the speed of sound.
- The reason is incorrect: The relative velocity of sound waves with respect to the person is not infinite; it is zero.

### Final Answer
The correct option is: Assertion is correct but reason is incorrect.

---