Answer. Refer to the diagram for clear visualization. 3. Sign Convention for Spherical Mirrors (Concave and Convex Mirrors) Distances are to be measured from the pole (vertex) of the mirror marked by point V in the figure. Sign convention for reflection of light through spherical lenses. In numericals, we need to calculate some things likeObject distanceImage distanceObject heightImage heightFocal lengthTo calculate them correctly, we need to find whether it is positive or negativeThe sign convention mentioned below helps us in itWe can see the sign convention in … In a spherical mirror: ... Derivation of lens formula or mirror equation; Sign Conventions. Sign Convention for Reflection by Spherical Mirrors . This sign convention is known as New cartesian sign convention. Those distances measured opposite to the direction of incidence light … According to the new Cartesian sign convention (figure 1) : (i) The pole ‘P’of the mirror is taken as the origin and the principal axis of the mirror is taken as the x-axis of the coordinate system. (ii) The distances measured in the same direction as that of incident light are taken as positive. This sign convention is known as New Cartesian Sign Convention. Distances measured along the direction of the incident ray are positive. Sign convention used in spherical mirrors The following sign convention is used for measuring various distances in the ray diagrams of spherical mirrors: Object is always placed to the left of mirror All distances are measured from the pole of the mirror. New Cartesian Sign Convention for spherical lenses: (i) All the distances are measured from the optical centre of the lens. According to it: Object is always placed to the left of mirror. This means sign is always taken as −( negative) in front of a spherical mirror. concave and convex mirrors. The distance measured opposite … Sign convention for reflection by spherical mirrors Reflection of light by spherical mirrors follow a set of sign conventions called the New Cartesian Sign Convention. The principal axis of the mirror is taken as the x-axis (X'X) of the coordinate system. For example; the distance of object is always taken as – (negative) in case of both types of spherical mirror, i.e. This means sign is always taken as −(negative) in front of a spherical mirror. 4. This means sign is always taken as – (negative) in front of a spherical mirror. All the distances measured along the direction of incident light (along +ve x-axis), are considered to be positive. Sign is taken as −( negative) from pole of a spherical mirror towards object along the principle axis. (iii) The distances measured against the direction of incident light are taken as negative. In this convention, the pole (P) of the mirror is taken as the origin. Sign is taken as −(negative) from pole of a spherical mirror towards object along the principle axis. 2. All distances are measured from the pole of the mirror. New Cartesian Sign Convention for spherical lenses: (i) All the distances are measured from the optical centre of the lens. For the measurement of all the distances, the optical center of the lens is considered. In this convention, the pole (P) of the mirror is taken as the origin. We will use the New Cartesian Sign Convention for the reflection of light by spherical mirrors. Sign is taken as – (negative) from pole of a spherical mirror towards object along the principal axis. Sign convention is a set of rules to set signs for image distance, object distance, focal length, etc for mathematical analysis of image formation. We can see the sign convention in both mirrors Some points to note Since focus of concave mirror is on the left side (in front of the mirror), Focal length of concave mirror is negative Since focus of convex mirror is on the right side (behind the mirror), Focal length of convex mirror is positive In this convention, the pole (P) of the mirror is takenat the origin of X -Y coordinate system. Sign conventions for reflection of light by spherical mirror are: 1. (ii) The distances measured in the same direction as that of incident light are taken as positive. The new Cartesian sign convention is used for measuring the various distances in the ray-diagrams of spherical mirrors. The conventions are as follows - Sign convention for reflection by spherical mirrors Reflection of light by spherical mirrors follow a set of sign conventions called the New Cartesian Sign Convention. (iii) The distances measured against the direction of incident light are taken as negative. The conventions are as follows – (i) The object is always placed to the left of the mirror. The principal axis of the mirror is taken as the x-axis (X'X) of the coordinate system. The object is always placed to the left of the mirror. New Cartesian Sign Convention is used to avoid confusion in understanding the ray directions. This sign convention is known as New cartesian sign convention. All the distances parallel to the principal axis are always measured from the pole of the spherical mirror.