Page 1 - Lesson-sign convention rules of spherical mirror
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SAI INTERNATIONAL SCHOOL
                                                      PHYSICS
                                                      CLASS X
                             Chapter: LIGHT(REFLECTION & REFRACTION)
                                                    MODULE-25



               LESSON NOTES:


               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. In this convention, the pole (P) of the mirror is
               taken as the origin. The principal axis of the mirror is taken as the x-axis (X'X) of the
               coordinate system. The conventions are as follows -


                     The object is always placed to the left of the mirror. This implies that the light
                       from the object falls on the mirror from the left-hand side.
                     All distances parallel to the principal axis are measured from the pole of the
                       mirror.
                     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.
                     Distances measured perpendicular to and above the principal axis (along + y-
                       axis) are taken as positive.
                     Distances measured perpendicular to and below the principal axis (along -y-
                       axis) are taken as negative.
               These new Cartesian sign convention for spherical mirrors are shown below in the


























               figure








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