What is the relationship between focal length and focal points?

[vetgirl1990]

Homework Statement

This is a silly question... but I know that a lens has two focal points but one focal length.
If each focal point is at 5cm from the lens, would the focal length be 5cm, or 10cm (adding the position of each focal point together)?

Homework Equations

N/A

The Attempt at a Solution

N/A

 

[bigguccisosa]

For a thin lens in air, the focal length is the distance from the center of the lens to the principal foci (or focal points) of the lens. So it would just be 5cm.
Taken from https://en.wikipedia.org/wiki/Focal_length