Question

The word “virtual” refers to something that exists in effect but not in actual fact. How does this definition relate to the virtual image you see of yourself in a plane mirror?

Answer 1

When you look in a plane mirror you see an image that your brain locates behind the glass. That image "exists in effect" because light rays coming from your body reflect off the mirror and enter your eye, producing the visual impression of a person located behind the mirror. It is "not in actual fact" because no light actually passes through or comes from that point behind the mirror — the reflected rays only appear to diverge from a point behind the glass when you extend them backward.

In optics terms: reflected rays reaching your eye are diverging; if you extend those rays backward they intersect at a point behind the mirror. That intersection is the virtual image. It cannot be projected onto a screen and you cannot touch it, even though you clearly see it — exactly matching the dictionary sense of "virtual."