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# Ray Diagram for Object Located at the Focal Point

Thus far we have seen via ray diagrams that a real image is produced when an object is located more than one focal length from a converging lens; and a virtual image is formed when an object is located less than one focal length from a converging lens (i.e., in front of F).

But what happens when the object is located at F? That is, what type of image is formed when the object is located exactly one focal length from a converging lens? Of course a ray diagram is always one tool to help find the answer to such a question. However, when a ray diagram is used for this case, an immediate difficulty is encountered. The diagram below shows two incident rays and their corresponding refracted rays.

For the case of the object located at the focal point (F), the light rays neither converge nor diverge after refracting through the lens. As shown in the diagram above, the refracted rays are traveling parallel to each other. Subsequently, the light rays will not converge to form a real image; nor can they be extended backwards on the opposite side of the lens to intersect to form a virtual image.

So how should the results of the ray diagram be interpreted? The answer: there is no image!! Surprisingly, when the object is located at the focal point, there is no location in space at which an observer can sight from which all the refracted rays appear to be coming. An image cannot be found when the object is located at the focal point of a converging lens.