Final answer:
The virtual image seen in a side mirror appears behind the mirror, the same size and upright, due to the law of reflection, creating an illusion of space.
Step-by-step explanation:
The image you see in a side mirror is a virtual image. It appears that this image is located behind the mirror, which is an effect of the law of reflection. The angles at which light is reflected into your eyes create the illusion that your image is the same distance behind the mirror as you are in front of it. In reality, no light is coming from behind the mirror; this is simply where the reflected rays appear to diverge from.
This optical phenomenon allows the image to maintain the same orientation and size as the actual object. Side mirrors on a car, for example, can make spaces appear larger than they are. Unlike real images, which are formed by the actual convergence of light rays, a virtual image cannot be projected onto a screen but can be captured by cameras and seen by our eyes.