Two lenses of power 2.5 D and 1.5 D are joined together. The power of the new lens formed is

Options

A. `3/5D`
B. `5/3D`
C. 4 D
D. 1 D

Explanation

To find the power of the new lens formed by joining two lenses with given powers, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Powers of the Lenses**:
- Let \( P_1 = 2.5 \, D \) (power of the first lens)
- Let \( P_2 = 1.5 \, D \) (power of the second lens)

2. **Use the Formula for Combined Power**:
- The total power \( P \) of two lenses in combination is given by the formula:
\[ P = P_1 + P_2 \]

3. **Substitute the Values**:
- Substitute the values of \( P_1 \) and \( P_2 \) into the formula:
\[ P = 2.5 \, D + 1.5 \, D \]

4. **Perform the Calculation**:
- Add the powers together:
\[ P = 4.0 \, D \]

5. **Conclusion**:
- The power of the new lens formed by joining the two lenses is \( 4.0 \, D \).

### Final Answer:
The power of the new lens formed is **4.0 Diopters**.

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