How an Image is formed by a plane mirror?
When you look in the mirror, you see your image at the other side of the mirror.

Each illuminated point on the object sends beams of light in all directions.

Light from the object arrive to the plane mirror, and each beam is reflected by the mirror according to the law of Reflection.

The image is seen at the place where the continuations of the reflected beams intercect.

To see interactively how an image is formed by a plane mirror click here.