Virtual image

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Top: The formation of a virtual image using a concave 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 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 formed by placing a screen at the position of the virtual image.

In optics, a virtual image is a representation of an actual (source) object that we see due to curving (converging or diverging) rays of light. No image can be captured using a screen where the virtual image seems to be, because, curved light rays don't draw the image on that plane (as opposed to a real image where curving rays actually draw a representation of the source object on a plane). A virtual image is the image of our face in a plane mirror. They are also called unreal images. A plane mirror always forms unreal images.

When we look through the lens or look into the convex or concave mirror what we see is a virtual image. What we get when we place a screen behind a convex lens or in front of a concave mirror what we see on the screen is a real image.

For example, a plane or convex mirror forms a virtual image positioned behind the mirror. Although rays of light seem to come from behind the mirror, light from the source spreads and exists only in front of the mirror. Virtual images are always represented by dotted lines.