Real image (such as the images on the right), real rays of light are always represented by full, solid lines; perceived or extrapolated rays of light are represented by dashed lines. A real image occurs where rays converge, whereas a virtual image occurs where rays only "appear" to converge. Real images can be produced by concave mirrors and converging lenses, only if the object is placed further away from the mirror/lens than the focal point and this real image is inverted. As the object approaches the focal point the image approaches infinity, and when the object passes the focal point the image
WHAT IF software the Dutch Center for Molecular and Biomolecular Informatics (CMBI) in Nijmegen, Netherlands. It is available for in-house use, or as a web-based resource. , the original paper describing WHAT IF has been cited more than 3,000 times. WHAT IF provides a flexible environment to display, manipulate, and analyze small molecules, proteins, nucleic acids, and their interactions. One notable use was detecting many millions of errors (often small, but sometimes catastrophic) in Protein Data Bank (PDB) files. WHAT IF also provides an environment for: homology modeling of protein tertiary structures and quaternary structures; validating protein structures, notably those deposited in the