Question

For an object at infinity, the focal length of a normal eye-lens is about

Answer 1

An optical system's focal length is a measurement of how strongly it converges or diverges light.

1. Because the distance between the eye lens and the retina is roughly $1.7cm$, a normal eye lens has a focal length of around $1.7cm$.
2. As a result, when parallel rays arrive, they form an image at focus, and the focal length of the picture at the retina should be around $1.7cm$.
3. Thus, for an object at infinity, the focal length of a normal eye lens is about $1.7cm$.