MadSci Network: Engineering
Query:

Re: making a magnifying device without a traditional lense.

Date: Tue Aug 14 07:50:22 2001
Posted By: Nial Tanvir, Faculty, Astrophysics, University of Hertfordshire
Area of science: Engineering
ID: 995948059.Eg
Message:

Hmm, where to start?!

Most optical instruments, such as telescopes, which use lenses
can be redesigned to use mirrors instead to collect and focus light.
This was first done by Newton - reflecting telescopes having some
advantages such as no chromatic aberration and ease of construction;
but some disadvantages such as having to arrange a more complicated
light path so that the observer does to block the light!

Simple ways of magnifying without "traditional" lenses would include
use of a drop of water, or other liquid - quite effective on a small
scale!  Another kind of non-traditional lens is the "fresnel lens" which
consists of concentric rings, a bit like a lens from which the solid
middle has been removed, and the whole thing squashed flat.  Probably
my description isn't very illuminating - but fortunately you can see
examples of such flat lenses in many over-head projectors and eg. devices
to help see the rear of your car while reversing!  The quality isn't very
good, but they are large, cheap and convenient.

I hope that gives you some food for thought!



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