CBSE Class 10 Answered

Sign Conventions for spherical Mirrors:

I. Objects are always placed to the left of the mirror i.e. light must fall on the mirror from left to right.

II. All distances are measured from the pole of the mirror.

III. Distances along the direction of the incident ray (along positive x- axis) are taken as positive, while distances along the direction of the reflected ray (along negative x-axis) are taken as negative.

IV. Heights measured perpendicular to and above the principal axis (along positive y-axis) are taken as positive.

V. Heights measured perpendicular to and below the principal axis (along negative y-axis) are taken as negative.

These sign conventions can also represented in the following diagram:

Sigh Convention for Lenses

I. Object is always placed to the left of the lens i.e., the light must fall on the lens from left to right.

II. All distances parallel to the principal axis are measured from the optical centre of the lens.

III. Distances along the direction of incident rays (along positive x-axis) are taken as positive, while distances opposite to the direction of incident rays (along negative x-axis) are taken as negative.

IV. Distances measured above the principal axis (along positive y-axis) are taken as positive.

V. Distances measured below the principal axis (along negative y-axis) are taken as negative.

These sign conventions are represented in the following diagram: