negative, it’s inverted. Because so is always positive, we can come to two
conclusions: If si is positive, then m is negative, so real images are always
inverted, and, if si is negative, then m is positive, so virtual images are always
upright.
Image Is Everything
Remember that all real
images are inverted and
all virtual images are
upright.Finally, to distinguish mathematically between concave and convex mirrors, we
always write the focal length f as a positive value for concave mirrors and a
negative value for convex mirrors. With these two equations and their
accompanying conventions, all four questions about an image can be answered. The
mirror equation answers questions (1) and (2), and the magnification equation
answers (3) and (4).