(A): Coulomb force between charges is central force
(R ): Coulomb force depends an medium between charges

Options

A. Both .A. and .R. are true and .R. is the correct explanation of .A.
B. Both .A. and .R. are tru and .R. is not the correct explanation of .A.
C. A. is true and .R. is false
D. A. is false and .R. is true

Answer

To solve the question regarding the assertion and reason provided, we will analyze both statements step by step.

### Step 1: Analyze the Assertion
The assertion states that "Coulomb force between charges is a central force."

- **Explanation**: A central force is defined as a force that acts along the line joining the two interacting bodies. In the case of Coulomb's law, the force between two point charges (let's say +q and -q) acts along the line connecting the two charges. The force is attractive if the charges are of opposite signs and repulsive if they are of the same sign. Therefore, the Coulomb force indeed acts along the line joining the two charges, making it a central force.

### Step 2: Analyze the Reason
The reason states that "Coulomb force depends on the medium between charges."

- **Explanation**: Coulomb's law is given by the formula:
\[ F = \frac{1}{4 \pi \epsilon_0} \frac{q_1 q_2}{r^2} \]
where \( \epsilon_0 \) is the permittivity of free space. When charges are placed in a medium other than a vacuum, the force is modified by the dielectric constant \( k \) of that medium. The modified formula becomes:
\[ F' = \frac{1}{4 \pi \epsilon_0 k} \frac{q_1 q_2}{r^2} \]
This shows that the force does indeed depend on the medium between the charges, as the dielectric constant \( k \) alters the effective force.

### Step 3: Conclusion
Both the assertion and the reason are true. However, the reason does not explain why the Coulomb force is a central force; it only states that the force depends on the medium. Therefore, while both statements are true, the reason does not provide a correct explanation for the assertion.

### Final Answer
- Assertion (A) is true.
- Reason (R) is true.
- However, R does not explain A.