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L7-21. Magnifying Glass - TV


To illustratre how a magnifying glass works.◙


TV camera, 20cm, 10cm and 5cm focusing lenses, and mounted rule on optical rail, TV monitor not shown

Setup Time

5 minutes.




The TV camera functions as the eye, so what the eye sees can be viewed on a monitor or the rear projection screen. First the focus is set at the near point of the TV lens (the near point of the eye), approximately 20 cm, and the ru le brought into focus as viewed on the monitor. The 20 cm focal length convex lens magnifying glass is then inserted as shown in the photo, the focus adjusted to infinity, and the object position adjusted slightly to obtain the best focus. The image size is the same! This demonstration illustrates that the function of a magnifying glass is not to "magnify" but to al


Lecture Demonstration Record Form. ◙Jay S. Huebner and Terry L. Smith, Why Magnification Works, TPT 32, 102-103 (1994).