Assertion `(A) :` In a Daniell cell, if the concentration of `Cu^(2+)` and `Zn^(2+)` ions are doubled, the `EMF` of the cell will be doubled.
Reason `(R) :` If the concentration of ions in contact with metals is doubled, the electrode potential is doubled.
(a)If both `(A)` and `(R)` are correct, and `(R)` is the correct explanation of `(A)`.
(b)If both `(A)` and `(R)` are correct, but `(R)` is not the correct explanation of `(A)`.
(c)If `(A)` is correct, but `(R)` is incorrect.
(d)If `(A)` is incorrect, `(R)` is correct.

Options

A. If both `(A)` and `(R)` are correct, and `(R)` is the correct explanation of `(A)`.
B. If both `(A)` and `(R)` are correct, but `(R)` is not the correct explanation of `(A)`.
C. If `(A)` is correct, but `(R)` is incorrect.
D. If `(A)` is incorrect, `(R)` is correct.

Answer

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

### Step 1: Understanding the Assertion (A)
The assertion states that in a Daniell cell, if the concentration of `Cu^(2+)` and `Zn^(2+)` ions are doubled, the EMF of the cell will also be doubled.

**Analysis**:
- The EMF (Electromotive Force) of a Daniell cell is determined by the Nernst equation, which states that the EMF is dependent on the concentration of the ions involved in the redox reaction.
- Specifically, the EMF is proportional to the difference in the electrode potentials of the two half-cells.
- If both concentrations are doubled, the ratio of the concentrations remains constant (since both the numerator and denominator are multiplied by the same factor).
- Therefore, the EMF does not change; it remains constant.

### Conclusion for Assertion (A):
**Assertion (A) is incorrect.**

### Step 2: Understanding the Reason (R)
The reason states that if the concentration of ions in contact with metals is doubled, the electrode potential is doubled.

**Analysis**:
- The electrode potential of a half-cell is indeed affected by the concentration of the ions in contact with the electrode, as described by the Nernst equation.
- If the concentration of the ions is doubled, the electrode potential will increase, but it does not necessarily mean it will double. It depends on the specific half-reaction and the conditions.
- Therefore, while the statement is partially correct, it is misleading because it implies a direct doubling of potential, which is not universally true.

### Conclusion for Reason (R):
**Reason (R) is incorrect.**

### Final Conclusion:
Since assertion (A) is incorrect and reason (R) is also incorrect, the correct answer is:
**(d) If (A) is incorrect, (R) is correct.**