Video Transcript
Light from an object is reflected
by a plane mirror. The mirror produces an image of the
object. Which of the following correctly
describes how the sizes of the object and its image compare? (A) The image is larger than the
object. (B) The image is smaller than the
object. (C) The image is the same size as
the object.
To see which answer is correct,
imagine we look at a plane mirror from the side. Since the mirror is plane, from
this perspective, it will look like a straight line. If an object is put in front of the
mirror and an observer looks at the mirror, then that observer will see light from
the object that is bounced off the mirror. By tracing those reflected light
rays backward, the observer can see an image of the object. Our question is, is that image
larger, smaller, or the same size as the object? Since we have here a plane mirror,
that is, a flat mirror, it will always reflect light so that the size of the image
matches the size of the object. That is, the image and the object
have the same size. If our mirror was not a plane
mirror, it might reflect light so that the image is not the same size as the
object. But because it is plane, they are
the same size.
