Video Transcript
The following figure shows light
rays being focused correctly by an eye. The object that the light comes
from is not shown. Are the light rays from a point on
a nearby object or from a point on a distant object? (A) The light rays are from a point
on a distant object. (B) The light rays are from a point
on a nearby object. (C) There is no way to tell.
This question is asking about
parallel light rays entering the eye from a point on an object some distance
away. It is asking us to determine if
this object is nearby, distant, or if there is no way to tell.
We know that two rays of light
traveling in the same direction are parallel to each other if they neither converge,
move closer together, or diverge, move farther apart. This is the case for the two light
rays entering the observer’s eye, which are parallel. We can construct a ray diagram
showing light rays from a point on a nearby object. Light from a point on a nearby
object will diverge. This means the light is not
parallel. So, option (B) cannot be the
correct answer.
An object that is very distant will
still emit diverging light rays from a point. If we zoom in on the observer’s eye
in this diagram, we can see that over very long distances these light rays will
appear parallel to each other. Because the light rays entering the
eye in our diagram are parallel, we can therefore determine that the object that the
light rays must be from is a distant object. So, the correct answer is option
(A).
