Virtual Images

Reflections of objects in plane mirrors are called virtual images. They are virtual because they appear to exist in space behind the mirror, and cannot be, for example, projected onto a screen. These images form at predictable locations based on the distance between the object and the mirror.

Light from an object 💎 that reflects off a mirror appears to originate from the direction it was traveling in when it reached the observer. Its distance appears the same as the distance traveled by the real ray. The solid lines indicate the path of light rays, while the dimmed lines indicate the perceived path from the virtual images.

Interestingly, this is not affected by the position of the observer. To prove this to yourself, try moving the observer 👁️ around the room, and notice what happens!

When two or more mirrors are present, light can take multiple paths to reach an observer, forming multiple images based on the principles above. Here we have a room with parallel mirrors on the left and right walls. You can see virtual rooms to the left and right of the real room.