(A) : The values of `in` and μ depend on the medium.
(R) : The electromagnetic force between two charges or magnets depends on the medium in which they are located.

Options

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

Answer

To solve the question, we need to analyze the two statements provided: the assertion (A) and the reason (R).

### Step-by-step Solution:

1. **Understanding the Assertion (A):**
- The assertion states that the values of ε (epsilon) and μ (mu) depend on the medium.
- Here, ε represents permittivity, and μ represents permeability.
- In general, the permittivity of a medium is given by the equation:
\[ \epsilon = \epsilon_0 \cdot k \]
where ε₀ is the permittivity of free space and k is the relative permittivity (dielectric constant) of the medium.
- Similarly, the permeability of a medium is defined as:
\[ \mu = \mu_0 \cdot m \]
where μ₀ is the permeability of free space and m is the relative permeability of the medium.
- Therefore, the assertion is **true** because both ε and μ indeed depend on the medium.

2. **Understanding the Reason (R):**
- The reason states that the electromagnetic force between two charges or magnets depends on the medium in which they are located.
- The force \( F \) between two point charges \( q_1 \) and \( q_2 \) separated by a distance \( r \) in a medium is given by:
\[ F = \frac{1}{4 \pi \epsilon} \cdot \frac{q_1 q_2}{r^2} \]
- As we can see, the force \( F \) is inversely proportional to ε, which varies with the medium.
- Thus, the electromagnetic force does depend on the medium, making the reason **true** as well.

3. **Determining the Relationship:**
- Now, we need to check if the reason is the correct explanation of the assertion.
- The assertion talks about the dependence of ε and μ on the medium, while the reason discusses how the force between charges or magnets is influenced by the medium.
- Since the force depends on ε (which is part of the assertion), the reason does provide a correct explanation for the assertion.

### Conclusion:
Both the assertion (A) and the reason (R) are true, and the reason is the correct explanation of the assertion. Therefore, the answer is:
**Option 1: Both A and R are true, and R is the correct explanation of A.**