Question

Difference between paraxial and marginal rays

Answer 1

While both paraxial and marginal rays are parallel to the principal axis, the basic difference lies in the distance between them and the principal axis. While paraxial rays are in close proximity to the principal axis , the marginal rays are further away.

These rays on refraction or reflection due to a spherical lens or a spherical mirror converge at or appear to diverge from different focii.

Answer 2

Paraxial and Marginal rays

Explanation:

A paraxial ray is a ray which makes a small angle to the optical axis of the system, and lies close to the axis throughout the system.  

Marginal rays are light rays that passes through an optical system away from the optical axis, towards the edge of the lens aperture.

Both paraxial and marginal rays are parallel to the principal axis, but the paraxial rays are much closer to the principal axis compared to the marginal rays. The focal point for these two type of rays are different.

Please refer to the picture attached for a diagrammatic representation of these two rays.