4. Consider a spherical refractor with water on one side (nwater = 1.33) and pyrex on the other (npyrex = 1.47). The object is placed in the water and the refracting surface looks convex from the object's side. The radius of the refracting surface is 0.5 m. a) What is the focal length of the spherical refractor? b) Determine the range of object distances for which the image is on the same side as the object (in the water) and the range of