I've got 3 arson questions for forensic science, answer what you can :) thanks

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?

Sort the images based on whether there's a force of attraction or repulsion between the magnets shown. attraction repulsion

Explain what will happen if decomposers were apsent from a forest ecoysystem.