Image Formation for Plane Mirrors
A GIF Animation
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 onject 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.
Additional information on physical descriptions of optical systems
will soon be available at The
Physics Classroom.
This page was created by Tom
Henderson of Glenbrook
South High School.
Comments and suggestions can be sent by e-mail to Tom
Henderson.
This page last updated on 8/29/97.