Final answer:
An upside-down image indicates that the mirror in question is a concave mirror, as opposed to a convex mirror, which always produces upright, smaller virtual images.
Step-by-step explanation:
If you see an upside-down image, the type of mirror you must be looking into is a concave mirror. Concave mirrors, which curve inward, can produce inverted images when the object is placed at a certain distance beyond the focal point. This is in contrast with convex mirrors, which are diverging mirrors and form images that are always virtual, upright, and smaller than the object.
A common example of a concave mirror is a makeup mirror, which is used to produce a larger, upright image when the object is within the focal length of the mirror. However, if you move further back, the mirror can produce an inverted image. On the other hand, the warning on car side mirrors, "Objects in the mirror are closer than they appear," is indicative of a convex mirror, which allows for a wider field of view but results in a smaller image that appears farther away.