1. The problem statement, all variables and given/known data At this site http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/micros.html , what does the negative sign indicate in the Mo formula? 2. Relevant equations On website 3. The attempt at a solution My guess is that either L or Fo are negative, but a negative magnification makes no sense, so basically it is a substitute for a modulus. Note: negative magnification could not possibly mean the image is diminished, because a diminished image simply has a magnification of less than 1 but greater than 0.