Answer:
Increase the radius of curvature of surface.
Explanation:
Radius of curvature is the measurement that is two times the focal length, for a given lens. It lies on either side of the lens.
Focal length is the distance which is half of the radius of curvature. Radius of curvature is a measure of the radius of the circle . Focal length is the distance between the center of curvature of the lens and the point where all the rays are brought to a focus for a distant object.
