How does the focal length of the lens change when looking at closely spaced objects?

The lens acts as a collecting lens, and the retina acts as a screen on which an image of an object is obtained. When the object approaches the converging lens (for distances longer than the focal length), the actual image of the object moves away from the lens. So that the position of the focused image of an approximate object relative to the center of the lens (lens) does not change, it is necessary to increase the optical power of the lens. The increase in optical power occurs due to an increase in the curvature of the lens. The focal length decreases (D = 1 / F).

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