Before revision: Similarly to curved mirrors, thin lenses follow a simple equation that determines the location of the images given a particular focal length () and object distance (): where is the distance associated with the image and is considered by convention to be negative if on the same side of the lens as the object and positive if on the opposite side of the lens.
After revision: Similarly to curved mirrors, thin lenses follow a simple equation that determines the location of the images given a particular focal length () and object distance where is the distance associated with the image and is considered by convention to be negative if on the same side of the lens as the object and positive if on the opposite side of the lens.