Question

state sign convention used to measure length of image and object​

Answer 1

sign convention used to measure length of image and object are:

1) The object is always placed to the left of the mirror .

2) All distances parallel to the principal axis are measured from the pole of the mirror.

3) All the distances measured to the right of the origin (along x axis) are taken as positive while those measured to the left of the origin (along -x-axis)are taken as negative.

4) Distance measured perpendicular to and above the principal axis ( along y axis )are taken as positive .

5) Distance measured perpendicular to and below the principal axis (along y axis )are taken as negative .

Hope the answer helps you a bit.