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Tutorial 3 - Algebraic Imaging through a Lens

This video I discuss imaging through a single optical surface and through a thin lens.

Please be aware that this video is intentionally confusing due to a lack of standard sign convention for imaging. If you really want to understand imaging see tutorial 4 for a description of an imaging nomograph, which is a mechanical model of lens imaging


  1. A real object 200 mm away from a 100 mm positive lens is imaged where? …. And with what magnification? 
  2. A virtual object is 30 mm inside a negative lens of focal length -100 mm. Where is the image? 
  3. The total track, or the object to image distance, is 139 mm. What is the focal length required to have a 2x magnification? Where is the lens located relative to the object? (Magnification hint: the image distance is twice the object distance) 
  4. (Extra Credit) Collimated light enters a ball of glass. What index of refraction will place the image on the back surface of the ball? (Hint: resembles a mirrors index)
Comment and discuss at YouTube!

Solutions here.