Positiv och negativ lins
Licens: By Lens2.png: Guam derivative work: Jfmelero (Lens2.png) [GFDL (www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (www.creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons
Linser
Positiv och negativ lins
Licens: By Lens2.png: Guam derivative work: Jfmelero (Lens2.png) [GFDL (www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (www.creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons
