Formation for Plane Mirrors
To view an object in any type of mirror, a person must sight along a line
at the image of the object. All persons capable of seeing the image must sight
along a line of sight directed towards the precise image location. As a person
sights in a mirror at the image of an object, there will be a reflected ray of
light coming from the mirror to that person's eye. The origin of this light ray
is the object. A multitude of light rays from the object are incident on the
mirror in a variety of directions; yet as you sight at the image, one of the
many rays will reflect off the mirror and travel to your eye. To see an object
in a mirror, you must sight at the image; and when you do a reflected ray of
light will travel from the mirror to your eye along your line of sight.
Not all people who are viewing the object in the mirror will sight along
the same geometrical line of sight. The precise direction of the sight line
depends on the location of the object, the location of the person, and the type
of mirror. Yet all of the lines of sight, regardless of their direction, will
pass through the image location. In fact, the image location is defined as the
location where reflected rays intersect. Since all people see a reflected ray
of light as they sight at an image in the mirror, then the image location must
be the intersection point of these reflected rays.
In the animation above, an object is positioned in front of a plane mirror.
The plane mirror will produce an image of the object on the opposite side of
the mirror. The distance from the object to the mirror equal the distance from
the image to the mirror. Any person viewing this image must sight at this image
position. The animation depicts the path of several rays of light from the
object to the mirror. This light subsequently reflects such that observers
could sight along a line of sight and view the image. Different people might
sight from different locations; yet each person would sight at the same image
location. As seen in the animation, the image location is the intersection
point of all the reflected rays.