Assertion: Stationary waves are so called because particles are at rest in stationary waves.
Reason: They are formed by the superposition of two identical waves travelling in opposite directions.

Options

A. (a)Both Assertion and Reason are true and the Reason is correct explanation of the Assertion.
B. (b)Both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
C. (c)Assertion is true, but the Reason is false.
D. (d)Assertion is false but the Reason is true.

Explanation

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

### Step 1: Understand the Assertion
The assertion states that "Stationary waves are so called because particles are at rest in stationary waves."

- **Analysis**: This statement is misleading. In stationary waves, particles do not remain completely at rest; rather, they oscillate about their mean position. Some points (nodes) do not move, but others (antinodes) do oscillate with maximum amplitude.

### Step 2: Understand the Reason
The reason states that "They are formed by the superposition of two identical waves traveling in opposite directions."

- **Analysis**: This statement is true. Stationary waves are indeed formed by the superposition of two waves of the same frequency and amplitude traveling in opposite directions. This superposition leads to the formation of nodes and antinodes.

### Step 3: Conclusion
Based on the analysis:
- The assertion is **false** because it incorrectly states that particles are at rest in stationary waves.
- The reason is **true** because it correctly describes how stationary waves are formed.

Thus, the correct conclusion is that the assertion is false, but the reason is true.

### Final Answer
The correct option is **D**: Assertion is false, Reason is true.

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