Some ray diagrams may also show a third ray. Peep holes contain concave lenses. They are set into doors so the occupant can identify a visitor before opening the door.

Some ray diagrams may also show a third ray. Only the person using the magnifying glass can see the image. The image cannot be projected onto a screen because it is a virtual image.

Here's what happens to the light ray diagram. That's a real image. The light rays actually cross at the point of the image. Your eye doesn't have to trick you into thinking the rays came from ...