Physicists are often asked why the image of an object, such as a chai

Physicists are often asked why the image of an
object, such as a chair, appears reversed left-to-right
rather than, say, top-to-bottom when viewed in a
mirror. Their answer is simply that an image viewed in
(5) a mirror appears reversed about the axis around which
the viewer rotates his or her field of sight in turning
from the object to its reflected image. That is, the
reversal in question is relative to the position and
orientation of the observer when the object is viewed
(10) directly. Since we ordinarily rotate our field of sight
about a vertical axis, mirror images usually appear
reversed left-to-right. This is the field-of-sight
explanation.

However, some physicists offer a completely
(15) different explanation of what mirrors “do,” suggesting
that mirrors actually reverse things front-to-back. If
we place a chair in front of a mirror we can envision
how its reflected image will appear by imagining
another chair in the space “inside” the mirror. The
(20) resulting reflection is identical to, and directly facing,
the original chair. The most notable thing about this
explanation is that it is clearly based on a false
premise: the chair “inside” the mirror is not real, yet
the explanation treats it as though it were as real and
(25) three dimensional as the original chair.

This explanation appeals strongly to many people,
however, because it is quite successful at explaining
what a mirror does—to a point. It seems natural
because we are accustomed to dealing with our mental
(30) constructs of objects rather than with the primary
sense perceptions on which those constructs are based.
In general, we can safely presume a fairly reliable
equation between our perceptions and their associated
mental constructs, but mirrors are an exception. They
(35) present us with sense perceptions that we naturally
construe in a way that is contrary to fact. Indeed,
mirrors are “designed” to make a two-dimensional
surface appear to have depth. Note, for example, that
mirrors are among the few objects on which we almost
(40) never focus our eyes; rather, we look into them,
with our focal lengths adjusted into the imagined space.

In addition to its intuitive appeal, the
front-to-back explanation is motivated in part by the
traditional desire in science to separate the observer
(45) from the phenomenon. Scientists like to think that
what mirrors do should be explainable without
reference to what the observer does (e.g., rotating a
field of sight). However, questions about the
appearances of images can be properly answered only if
(50) we consider both what mirrors do and what happens
when we look into mirrors. If we remove the observer
from consideration, we are no longer addressing
images and appearances, because an image entails an
observer and a point of view.

1. The main point of the passage is that an adequate explanation of mirror images

(A) must include two particular elements
(B) has yet to be determined
(C) must be determined by physicists
(D) is still subject to debate
(E) is extremely complicated


2. According to the passage, the left-to-right reversal of objects reflected in mirrors is

(A) a result of the front-to-back reversal of objects reflected in mirrors
(B) a result of the fact that we ordinarily rotate our field of sight about a vertical axis
(C) explained by the size and position of the object reflected in the mirror
(D) explained by the difference between twodimensional and three-dimensional objects
(E) explained by the mental constructs of those who observe objects reflected in mirrors


3. According to the passage, the fact that we are accustomed to dealing with our mental constructs rather than the primary sense perceptions on which those constructs are based facilitates our ability to

(A) accept the top-to-bottom explanation of what mirrors do
(B) understand the front-to-back explanation of what mirrors do
(C) challenge complex explanations of common perceptual observations
(D) reject customarily reliable equations between perceptions and their associated mental constructs
(E) overemphasize the fact that mirrors simulate sense impressions of objects


4. It can be inferred that the author of the passage believes that the front-to-back explanation of what mirrors do is

(A) successful because it is based on incongruous facts that can be reconciled
(B) successful because it rejects any consideration of mental constructs
(C) successful because it involves the rotation of a field of sight about an axis
(D) successful only to a point because it is consistent with the traditional explanations that physicists have offered
(E) successful only to a point because it does not include what happens when we look into a mirror


5. In the passage the author is primarily concerned with doing which one of the following?

(A) evaluating the experimental evidence for and against two diametrically opposed explanations of a given phenomenon
(B) demonstrating that different explanations of the same phenomenon are based on different empirical observations
(C) describing the difficulties that must be overcome if a satisfactory explanation of a phenomenon is to be found
(D) showing why one explanation of a phenomenon falls short in explaining the phenomenon
(E) relating the theoretical support for an explanation of a phenomenon to the acceptance of that explanation


6. With which one of the following statements would the author of the passage be most likely to agree?

(A) The failure of one recent explanation of what mirrors do illustrates the need for better optical equipment in future experiments with mirrors.
(B) Explanations of what mirrors do generally fail because physicists overlook the differences between objects and reflections of objects.
(C) One explanation of what mirrors do reveals the traditional tendency of physicists to separate a phenomenon to be explained from the observer of the phenomenon.
(D) The degree to which human beings tend to deal directly with mental constructs rather than with primary sense perceptions depends on their training in the sciences.


7. The author would be most likely to agree with which one of the following statements about the field-of-sight explanation of what mirrors do?

(A) This explanation is based on the traditional desire of physicists to simplify the explanation of what mirrors do.
(B) This explanation does not depend on the false premise that images in mirrors have threedimensional properties.
(C) This explanation fails to take into account the point of view and orientation of someone who is observing reflections in the mirror.
(D) This explanation assumes that people who see something in a mirror do not understand the reality of what they see.
(E) This explanation is unsuccessful because it involves claims about how people rotate their field of sight rather than claims about what people can imagine.


8. The author mentions the fact that we rarely focus our eyes on mirrors (lines 39–40) primarily in order to

(A) contrast our capacity to perceive objects with our capacity to imagine objects
(B) emphasize that it is impossible to perceive reflected objects without using mental constructs of the objects
(C) clarify the idea that mirrors simulate threedimensional reality
(D) illustrate the fact that we typically deal directly with mental constructs rather than with perceptions
(E) emphasize the degree to which the psychological activity of the observer modifies the shape of the object being perceived