Re: Diverging lenses

["John S. Denker" <jsd@MONMOUTH.COM>]

At 01:54 PM 5/14/01 -0400, Tim O'Donnell wrote:
> Other than vision correction, is there other common uses
> for diverging lenses?

Interesting question.  Answers include:

1) The world's first telescopes used a diverging lens for the eyepiece.
  http://fermi.bgsu.edu/~stoner/P202/device/sld010.htm

2) Even today, the simplest telescope uses a diverginge lens for the
eyepiece.  One advantage (in addition to extreme simplicity) is that this
produces a non-inverted image.  (Modern high-quality eyepieces are quite
complex, but to first order are converging lenses, resulting in an inverted
image.)
  http://fermi.bgsu.edu/~stoner/P202/device/sld011.htm

3) An achromatic lens can be considered a combination of two sub-lenses
  -- a crown-glass converging lens, plus
  -- a flint-glass diverging lens.
  http://www.utmem.edu/~thjones/hist/c5.htm

*) I'm sure there are many other interesting uses..........