Physics
Mirror Image
Quick fact
When you wave your right hand, the mirror image waves its left hand — but if you stand sideways, the mirror image does not swap up and down, only left and right.
Why this is interesting
You've seen your face in a mirror thousands of times, but have you ever wondered why your left hand appears to be on the right side of the reflection?
Read the full explanation
Understanding Mirror Image
A mirror image is what you see when light rays bounce off a flat, smooth surface like a mirror. The image appears to be behind the mirror at the same distance as the object is in front of it. This is called a virtual image because the light rays don't actually come from behind the mirror; your brain interprets them as if they do. Step by step: light from each point on the object strikes the mirror and reflects at the same angle. Your eyes trace those rays backward in straight lines, and they converge at a point behind the mirror. That point forms the image. The image is the same size as the object, upright, but reversed left to right — a phenomenon known as lateral inversion.
A deeper explanation
The mechanism behind a mirror image is the law of reflection: the angle of incidence equals the angle of reflection. For a plane mirror, the surface is perfectly flat, so each ray reflects predictably. The image is virtual because the reflected rays diverge, and your eye's lens refocuses them to form an image on your retina. Lateral inversion occurs because the mirror reverses the front-back axis, not left-right. When you face a mirror, your left hand is on the same side of the mirror as your actual right hand, causing the apparent swap. This concept matters because it reveals how we perceive depth and orientation through reflected light, and it underpins technologies from periscopes to rear-view mirrors.