Question

why a ray of light through the optical centre passes without any deviation in lenses

Answer 1

The ray passing through optical center does no 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 ie incident ray will be parallel to emergent ray but displaced. 

Answer 2

Answer:

1. The portion of a lens near the optical centre is like a very thin slab of glass.

2. Hence, a ray of light through the optical centre passes without any deviation in lenses.

Explanation:

Optical Centre :

1. The point inside a lens on the principle axis, through which light rays pass without changing their path is called the optical centre of a lens.

2. It is denoted by O.