Question

0 Object distance (u), image distance (v), focal length (f) are all measured from
(1) focus (F)
(2) optic centre (P)
(3) centre of curvatur (c)​

Answer 1

Answer:

focus-F

optic centre-P

centre of curvator-c

Answer 2

Answer:

All the distances are always measured from the optic centre.

Explanation:

Object distance(u) is the distance between the position of the object and the optic centre.

Image distance(i) is the distance between the position of the image and the optic centre.

Focal length(f) is the distance between the principal focus and the optic centre.

Optic centre(P) is the centre point of mirror or lens that lies on the principal axis, through which any light ray pass through without deviation.

Therefore, all the distances are always measured from the optic centre.

So, the correct answer is option (2)