What is the relationship between distance from the magnet and the strength of its magnetic field

Acurve connects the data points that are plotted. (physical science chapter 11 motion)

In a simplified model of the human eye, the aqueous and vitreous humors and the lens all have a refractive index of 1.40, and all the refraction occurs at the cornea, whose vertex is 2.60 cm from the retina. what should be the radius of curvature of the cornea such that the image of an object 40.0 cm from the cornea’s vertex is focused on the retina?

In an experiment, how can i change human errors? be specific.