You probably look at your image in the mirror almost every morning. What you see in the mirror is an exact replica of you and your surroundings. You move your finger and your image move sits finger in exactly the same way. It seems your mirror has accomplished the amazing feat of duplicating objects. The mirror, however, has accomplished nothing. This duplication is the result of your eyes interpreting the light property of reflection.
Reflection occurs when a light ray travels from an object (such as your body), hits a reflective surface (such as a mirror) and is redirected to your eye. It is the redirection of the light that causes a duplicate image to be created. When light hits a flat, reflective surface, it hits at a specific angle. This angle in which the light strikes the surface is called the angle of incidence. This angle is measured from the surface's normal, an imaginary line that lies perpendicular to the surface. Upon hitting the surface the light ray reflects, or bounces, off of the surface at an angle called the angle of reflection. The angle of reflection, like the angle of incidence, is also measured from the normal. By the laws optics, this angle is always identical to the angle of incidence.
When you look into a full length mirror, you are able to see a room identical to the one in which you are standing. In the room of the mirror you can even perceive depth just as it appears in the actual room. Our eyes can create depth because a light ray reflected by the mirror from an object in the room reaches your eye at the same angle from which a ray from the virtual image in the mirror appears to be originating. This concept may be easier to grasp using the following example and diagram:
On the right side of this diagram there is a man standing in front of a mirror with an orange sitting by his feet. When the man looks in the mirror he sees the reflection of the orange located at his reflection of his feet. Everything in the reflected image is positioned exactly as in the man's reality. Light rays from the orange reflect off of the mirror and reach the man's eyes, following the path of the green lines in the diagram. If there was actually an orange where the virtual image appears, light rays would reach the man along the path of the dotted red lines. The path of the dotted red lines matches the path of the solid green lines. Because the man's brain knows that light usually travels in a straight line, the light appears to be following the red lines so the brain misinterprets the signals and "sees" the image behind the mirror.
You can have a lot of fun playing with the property of reflection. Although reflection sometimes appears to be a miraculous trick, it is only a simple optical principle and a misinterpretation of light.