Duduli

Answer:- If  cardinal points are known, one can find the image of any object without making a detailed study of the passage of the rays through the system i.e it is not necessary to consider the refraction of the rays at the various surfaces.

Answer:- The first focal point is a point on the principal axis of the lens such that a beam of light passing through it is rendered parallel to the principal axis after refraction through the lens.

Answer:- Nodal points are points on the principal axis of the optical system where light rays, without refraction, intersect the optic axis.