Video Transcript
The following figure shows three
parallel light rays incident on a concave mirror. Which of the following is the term
for point P, which is shown by the black dot? (A) Center of curvature of the
mirror or (B) focal point of the mirror.
To answer this question, let’s
recall what the terms given in the answer choices mean, center of curvature and
focal point. The center of curvature of a mirror
is a point that is at the same distance from the surface of the mirror in any
direction. To determine if point P is the
center of curvature, we can draw new lines from P to different parts of the surface
of the mirror and compare their lengths. It’s clear that these two lines
have different lengths. Therefore, we can say that point P
is not the center of curvature.
Meanwhile, the focal point of a
curved mirror is a point at which the reflected rays of parallel incident rays all
cross each other’s paths. We can see that all the incident
rays are parallel. We also see that all the reflected
rays’ paths cross at point P. Therefore, the answer is (B). Point P is the focal point of the
mirror.
