I cannot seem to get the concept of real and virtual image. This is my understanding. If the light beams go to the reflecting surface(concave or convex mirror) then an image will be form assuming the reflecting beams meat at a point. If the image appears to be in front of the mirror(s' is positive) then the image is real. If the image appears to be behind the mirror(s' is negative) the image is virtual. Am I correct on this? When reading an example from my textbook about image formation by refraction. A light coming from air and going into a convex surface(left to right). s' ended up being positive and to the right of the refracting surface. Shouldn't the image be on the same side as the actual object since s' is positive? Some help would be appreciated.