Assertion: When a wave travels from a denser medium to rarer medium, then ampltitude of oscillation increases.
Reason: In denser medium, speed of wave is less compared to a rarer medium.

Options

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

Explanation

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

### Step 1: Understand the Assertion
The assertion states that when a wave travels from a denser medium to a rarer medium, the amplitude of oscillation increases.

**Explanation**:
In a denser medium, particles are closely packed, which typically results in a lower speed of wave propagation. When the wave transitions to a rarer medium, where particles are more spread out, the speed of the wave increases.

### Step 2: Understand the Reason
The reason provided states that in a denser medium, the speed of the wave is less compared to a rarer medium.

**Explanation**:
This is a fundamental property of wave propagation. The speed of a wave is generally lower in denser materials due to the greater mass and tighter packing of particles, which requires more energy to displace them. In contrast, in a rarer medium, particles can move more freely, allowing the wave to travel faster.

### Step 3: Analyze the Relationship Between Amplitude and Medium
To analyze how amplitude changes when moving from a denser to a rarer medium, we can use the formula for amplitude:

\[ \frac{A_2}{A_1} = \frac{2v_2}{v_1 + v_2} \]

Where:
- \(A_2\) is the amplitude in the rarer medium.
- \(A_1\) is the amplitude in the denser medium.
- \(v_1\) is the speed of the wave in the denser medium.
- \(v_2\) is the speed of the wave in the rarer medium.

### Step 4: Compare the Speeds
Since we know from the reason that \(v_1 < v_2\) (the speed in the denser medium is less than that in the rarer medium), we can conclude:

\[ A_2 > A_1 \]

This means that the amplitude in the rarer medium is indeed greater than the amplitude in the denser medium.

### Conclusion
Both the assertion and the reason are true. The assertion is true because the amplitude increases when moving from a denser to a rarer medium, and the reason is true as it correctly explains the relationship between wave speed in different media.

### Final Answer
- Assertion: True
- Reason: True
- Both are correct and the reason is the correct explanation of the assertion.

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