The focal length of a lens with power 2.5 D is …………………..

Explanation

To find the focal length of a lens with a power of 2.5 D (diopters), we can use the relationship between power and focal length.

### Step-by-Step Solution:

1. **Understand the relationship between power and focal length**:
The power \( P \) of a lens is defined as the reciprocal of its focal length \( f \) in meters:
\[
P = \frac{1}{f}
...