How could you identify the unmarked poles of a magnet? a. observe the concentration of field lines. b. put a magnet with known poles nearby. c. sprinkle iron fillings nearby and observe the field lines. d. put an iron nail nearby, with its head facing one pole.

If the radius of curvature of the cornea is 0.75 cm when the eye is focusing on an object 36.0 cm from the cornea vertex and the indexes of refraction are as described before, what is the distance from the cornea vertex to the retina? express your answer to two significant