Hi. "A biconvеx lеns has a focal length of 100mm. an object is placеd at distancеs of 150 mm and 75 mm from teh lens. Sketch a ray diagram to find the position of thе respective images. confirm these positiones via calculatinons. This is the diagram I have drawn: http://www.freewebs.com/questionsuk/diagram.JPG Does this seem ok? However, what equations would be used to confirm the position? Any help is appreciated.