Question

Dear Sir,
While I was dealing with the ray diagrams of refraction of lenses, this doubt arose in mind.
Why does a ray of light pass through the optic center without deviation, even though it goes through another medium of refractive index greater than air that is glass also it does not incline at an angle of 90 degrees.
According to refraction, it is supposed to be refracted and pass coincidently on the principal axis.
Please answer, thank you

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.