What is the result when an incident ray travels parallel to the axis of a lens?

When an incident ray travels parallel to the axis of a lens, it will refract through the principal focus after passing through the lens. This is a fundamental property of lenses, specifically convex lenses, which are designed to converge light rays.

As the parallel ray enters the lens, the shape of the lens causes it to bend towards the optical axis, specifically towards the point known as the principal focus. This focus is located on the opposite side of the lens from where the light originally enters. The refractive properties of the lens facilitate this bending of light, enabling the lens to bring the parallel rays to a single point of convergence.

This behavior is essential in applications such as cameras and magnifying glasses, where focusing light onto a specific point is necessary for creating clear images. The other choices do not accurately describe what happens when a ray of light travels parallel to the optical axis of a lens.