Re: how do you find the center of curvature and focal point with an experiment

For a simple lens, the center of curvature should be the geometric center
of the lens.

To find the focal length, utilize the following setup:

           
            |                                             |
{}----------|--------------------------()-----------------|--
light    paper with a small hole       lens             paper to view
source                                                   image

With an object (small hole) at infinity, parallel light rays will travel
through the lens and come to focus at a distance = focal length.
Simply move the paper on the right to view a sharp image of the small
hole from the paper on the left.  To close or too far away, the image
will be fuzzy.  When it is sharp and clear, the distance from the lens
to the image will be the focal length.
If your light source and object are close to the lens and not at "infinity"
You may calculate various parameters for a simple thin lens by using
   1/f = 1/do + 1/di
Where f = focal length, do = object distance from the lens, and
di = image distance from the lens.  Using these parameters you can also 
find the magnification as m = -di/do.