Question

Why doesn't a ray of light passing through the optical centre of a lens deviate?

Answer 1

The ray passing through optical centre does not deviate because the curvature of the Lens at the incident and exit point are exactly opposite so the deviation at the first point is cancelled at the other point. Note that for a thin lens the ray appears to be passing straight but for a thick Lens there will be a lateral shift i.e incident ray will be parallel to emergent ray but displaced.