Actually, without lenses, we would not know nearly as much about light and other sciences as we do now.
The key to lenses is an idea called Fermat's Principle. Fermat's
Principle says that light will take the path that minimizes the time of
travel. If you work through all the math (trust me because I've done it
at least 5 times), you get the equations that describe how a lens
works. In fact, very similar principles of minimization can be used to
derive the laws governing mechanical motion, and they play a key role
in formulating quantum mechanical descriptions of the same systems.
Lenses provide a convenient, accessible example of some of the deepest
principles of physics.
Lenses are then used to gather and focus light. For example, we can
gather a lot of light from a very distant object and focus it all into
our eyes. This is how a telescope works. A similar idea leads to
microscopes. Both telescopes and microscopes have been vital in
understanding many parts of science.
The benefit doesn't stop with lenses. You can carry it further to
fiber optic communication, which in the backbone of the Internet and
other communication systems. The same equations we used to understand
the lens can be modified to transmit data down a tiny glass fiber with
next to no loss.
As for understanding light, the lens still has importance. Many
things that we learn about light require a very very long distance (to
infinity works best) in order for us to use and experiment with. As my
coherent optics professor likes to say, "Lenses bring Infinity closer."
By using lenses, we can compress a system down in order to understand
the wave nature of light better where we wouldn't have had the space to
So, yes, lenses have had a profound impact on our understanding of
light and of other things in science. However, they tend to stay more
in the background and are easily overlooked.
(and where would many of us be without our glasses?)
Adam (and Tom)
(republished on 07/29/06)