How to construct
The solution is hidden. Draw your own rays with the Line (L) and Construct (C) tools, place your answer with Mark (X) when finding an image, then Check (E). Construction lines are dotted and infinite, bold lines are solid segments; both snap to F, O, S, C, intersections (also with the focal planes), the lens or mirror itself, the point where the given ray hits the element, and the directions parallel to the axis, parallel to the given ray and through a point. On a mirror, a line started at the vertex S also snaps to the mirror image (about the axis) of a line ending there; hold Shift to turn this off briefly. On a touch screen, press, slide to the snap point and release to place each point.