Video Transcript
Which of the mirrors below is a
spherical convex mirror? Incident light is shown by the
yellow lines.
This question is asking us to
identify a spherical convex mirror. Therefore, to answer this question,
there are two properties we need to recognize: which of these options are spherical
mirrors and which are convex mirrors. Both of these need to be true for
an answer to be correct.
We call mirrors spherical because
of their shape. If we traced out the curve of a
spherical mirror, we would find that it is a part of a larger sphere. We can eliminate some of the
options in the question by tracing out the curved paths the mirrors follow.
Options (D) and (B) do not trace
out a spherical shape and instead follow an oval path. These cannot be the correct answer,
as they are not spherical mirrors. Option (A) traces out a spherical
shape and so is a spherical mirror. Option (C) also traces out a
spherical shape and so is also a spherical mirror. They both have a radius of
curvature, which is the radius of the sphere we traced out. The center of curvature is the
center of this sphere. Every spherical mirror has a center
of curvature.
A convex mirror is a spherical
mirror with a particular curvature. The part of the mirror on the
optical axis is closer to the observer than the edges of the mirror. In other words, it curves towards
an observer. This means that for all convex
mirrors, the center of curvature will be on the opposite side of the mirror to the
observer.
If we label the observer and the
center of curvature in options (A) and (C), we can see that for option (A) they are
on the same side of the mirror. This means that while option (A) is
a spherical mirror, it is not convex; the mirror curves away from the observer. For option (C), the center of
curvature and the observer are on opposite sides. So option (C) is both a spherical
and a convex mirror as the mirror curves towards the observer. Therefore, option (C) is the
correct answer.
