A virtual image is an image formed at a point from which light rays appear to diverge but do not actually pass through. It cannot be projected onto a screen.
How a virtual image forms
When light rays reflect off a plane mirror, they diverge. Your brain traces these diverging rays backward in straight lines. The point where the extended rays appear to meet is the location of the virtual image. The light does not actually come from that point; it only appears to.
Virtual vs real images
| Property | Virtual image | Real image |
|---|---|---|
| Light rays | Appear to diverge from the image | Actually converge at the image |
| Screen | Cannot be caught on a screen | Can be caught on a screen |
| Formation | Behind a mirror, or on the same side as the object for a lens | In front of a mirror, or on the opposite side of a lens from the object |
| Orientation | Upright (for single mirror/lens) | Inverted (for single converging lens/concave mirror) |
Where virtual images form
Plane mirror: the virtual image forms behind the mirror at the same distance as the object is in front. It is the same size, upright, and laterally inverted.
Converging lens (object inside F): when the object is placed between the focal point and the lens, the lens cannot converge the rays. The diverging rays appear to come from a magnified, upright virtual image on the same side as the object. This is how a magnifying glass works.
Convex mirror and diverging lens: these always produce virtual images (for real objects) because they spread light out rather than focusing it.
In ray diagrams
A virtual image is shown using dashed lines for the extended rays. The image itself is drawn at the point where these dashed lines meet. Real images use solid lines because the light actually passes through the image point.
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