A: Speed of light in a medium is independent of the motion of the source relative to the medium.
R: Speed of light in a medium depends on the motion of the observer relative to the medium.

Options

A. IF both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark(2)
C. IF Assertion is true statement but Reason is false then mark(3)
D. If both Assertion and Reason are false statements, then mark (4)

Answer

To solve the question, we need to analyze both the assertion (A) and the reason (R) given in the problem statement.

### Step-by-Step Solution:

1. **Understanding Assertion (A)**:
- The assertion states that "the speed of light in a medium is independent of the motion of the source relative to the medium."
- This is true because the speed of light in a medium is determined by the properties of that medium, specifically its refractive index (μ). The speed of light in a medium is given by the formula:
\[ v = \frac{c}{\mu} \]
where \(c\) is the speed of light in a vacuum, and \(\mu\) is the refractive index of the medium. The motion of the source does not affect this speed.

2. **Understanding Reason (R)**:
- The reason states that "the speed of light in a medium depends on the motion of the observer relative to the medium."
- This statement is also true. When an observer moves relative to the medium, the speed of light observed by the observer can change due to the relative motion. The effective speed of light as perceived by the observer can be calculated using:
\[ v' = v - v_o \]
where \(v'\) is the observed speed of light, \(v\) is the speed of light in the medium, and \(v_o\) is the velocity of the observer.

3. **Analyzing the Relationship**:
- While both the assertion and the reason are true, the reason does not explain the assertion. The assertion is about the independence of the speed of light from the source's motion, while the reason discusses the observer's motion affecting the perceived speed of light.

4. **Conclusion**:
- Since both statements are true but the reason does not explain the assertion, the correct answer is that the assertion is true, the reason is true, but the reason does not support the assertion.

### Final Answer:
The answer is option 2: Assertion is true, Reason is true, but Reason does not explain Assertion.