Top: The formation of a virtual image using a diverging lens. Bottom: The formation of a virtual image using a convex mirror. In both diagrams, f is the focal point, O is the object and I is the image, shown in grey. Solid blue lines indicate light rays. It can be seen on the right that the light rays appear to emanate from the virtual image but do not actually exist at the position of the virtual image. Thus an image cannot be seen by placing a screen at the position of the virtual image.
