Assertion : Doppler effect is not observed in case of supersonic waves.
Reason : Waves produced by supersonic sources are shock waves which produce a sound.

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 regarding the assertion and reason about the Doppler effect and supersonic waves, we can break it down into the following steps:

### Step 1: Understand the Assertion
The assertion states that "Doppler effect is not observed in case of supersonic waves."
- **Explanation**: The Doppler effect refers to the change in frequency or wavelength of a wave in relation to an observer moving relative to the wave source. In the case of supersonic waves, the source of sound is moving faster than the speed of sound, which leads to a unique situation where the usual Doppler effect does not apply.

### Step 2: Understand the Reason
The reason states that "Waves produced by supersonic sources are shock waves which produce a sound."
- **Explanation**: When an object moves faster than the speed of sound, it creates shock waves instead of regular sound waves. These shock waves are a result of the compression of sound waves in front of the object, forming a conical shape. The sound we hear from these shock waves is not affected by the Doppler effect in the same way as regular sound waves.

### Step 3: Analyze the Doppler Effect Formula
The Doppler effect can be analyzed using the formula:
\[ f' = f_0 \frac{v - v_o}{v - v_s} \]
Where:
- \( f' \) = observed frequency
- \( f_0 \) = source frequency
- \( v \) = speed of sound
- \( v_o \) = speed of the observer
- \( v_s \) = speed of the source

In the case of a supersonic source:
- \( v_s > v \) (the speed of the source is greater than the speed of sound).
- If we substitute \( v_s \) into the formula, it leads to a situation where the observed frequency becomes negative, which is not physically meaningful.

### Step 4: Conclusion
Based on the above analysis:
- The assertion is correct: Doppler effect is not observed in supersonic waves.
- The reason is also correct: Supersonic sources produce shock waves, which do not exhibit the Doppler effect in the typical sense.

### Final Answer
Both the assertion and reason are correct, and the reason correctly explains the assertion.

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