Question

A ray of light passing through the optical centre of the lens does not deviate from its path after refraction. Explain.

Answer 1

A ray of light passing through the optical centre of a thin lens does not deviate because the central part of the lens behaves like a very thin rectangular glass slab with parallel faces. When a light ray enters and exits two parallel surfaces, it undergoes a slight lateral displacement (sideward shift) rather than a change in its direction (angular deviation). For a thin lens, the thickness at the center is negligibly small, making this lateral shift practically zero. Therefore, the light ray passes straight through the optical center without any noticeable deviation from its original path.