How do rays parallel to the principal axis behave after reflection from a convex mirror?

The correct option is: They appear to diverge from a point on the principal axis.

Let us understand the behavior of light rays when they reflect off a convex mirror step-by-step:

1. Structure of a Convex Mirror:
A convex mirror is a spherical mirror whose reflecting surface curves outwards, away from the center of the sphere from which it is cut. The center of curvature and the principal focus lie behind the reflecting surface of the mirror.

2. Reflection of Parallel Rays:
When a beam of light rays traveling parallel to the principal axis strikes the reflecting surface of a convex mirror, they undergo reflection according to the laws of reflection. Because of the outward curvature of the mirror, the reflected rays are spread out, or diverged, in different directions.

3. The Principal Focus:
If we trace these diverged reflected rays backward behind the mirror, they all appear to meet or intersect at a single point on the principal axis. This point is called the principal focus (F) of the convex mirror. Since the rays do not actually meet but only appear to do so, we say that the parallel rays appear to diverge from this point (the focus) on the principal axis after reflection.