Final answer:
A virtual image is formed from the apparent divergence of light rays and cannot be projected onto a screen; it is typically seen upright and magnified, such as in a flat mirror or through a magnifying glass.
Step-by-step explanation:
The term virtual image refers to a type of image that is formed by the apparent divergence of light rays from a point. Unlike a real image, a virtual image cannot be projected onto a screen because it does not actually come from a real location in space. Virtual images are formed when the outgoing rays from an object diverge; a viewer perceives these rays as converging at a point behind the optical device (such as a lens or mirror), thus seeing an image in a location where no light actually exists.
To further clarify with an example, when you look at yourself in a flat mirror, the image you see is a virtual image. It appears to be behind the mirror, but it's not something that could be captured on a screen placed at that location behind the mirror. This is because the light rays are not actually converging there; they only seem to do so when traced back in straight lines into the mirror.
Virtual images are typically upright and the same size or magnified compared to the object, depending on the specific optics involved. For example, the image is virtual, upright, and magnified when seen through a magnifying glass, which is a convex lens.