Sign Convention for Reflection by Spherical Mirrors Video Lecture - Science

sign convention for spherical lenses the
new Cartesian sign conventions for
measuring various distances or heights
in case of lenses are similar to the one
used for spherical mirrors all the
distances in lenses are measured from
the optical centre of the lenses
according to the convention the focal
length of a convex lens is positive and
that of a concave lens is negative
according to the new Cartesian sign
conventions the optical center of the
lens is taken as the origin the
principal axis of the lens is taken as
the x-axis X - X of the coordinate
system the object is always placed to
the left side of the lens and light is
incident on the lens from the left to
the right all distances parallel to the
principal axis or measured from the
optical center of the lens's all the
distances measured to the right of the
optical centre along + x axis are taken
as positive while those measured to the
left of the optical centre along minus x
axis are taken as negative the height
measured upwards perpendicular to the
principal axis along + y axis of the
lens is taken as positive the height
measured downwards perpendicular to the
principal axis along minus y axis of the
lens is taken as negative