the questions is The left end of a long glass rod in diameter has a convex hemispherical surface in radius. The refractive index of the glass is . Distances are measured from the vertex of the hemispherical surface (to the right is positive for image distances). Determine the position of the image if an object is placed in air on the axis of the rod at the infinitely far distance to the left of the vertex of the curved end. do i use 1/d+1/d_i=1/f??? or i use something else? i plug in 1/d which d is infinity, so its 0, but i didnt get the right answer. can anyone help?