A ray is aimed at the exact centre of a thin lens, either converging or diverging. What happens to it?

1. A ray passing through the centre of either a converging or a diverging lens does not change direction. 2. At the centre the two lens faces are effectively parallel, so the ray is deflected by a negligible amount. 3. This makes the central ray the easiest of all to draw in a ray diagram. 4. Bending through the focal point is what happens to a ray that arrives parallel to the axis, not to a central ray. _Source: OpenStax College Physics (CC BY 4.0), Ch 25 "Geometric Optics", section 25.6 Image Formation by Lenses_