Re: [Phys-l] A demo for biologists?

[ludwik kowalski <kowalskil@mail.montclair.edu>]

P.S.
A single expended beam seems to be a better, and simpler to implement,  
approach.

Ludwik


On May 15, 2009, at 11:00 AM, ludwik kowalski wrote:

> On May 14, 2009, at 5:33 PM, John Clement wrote:
>
> > > Rumor around here is that hypothesis testing as "the scientific
> > > method"
> > > originated with the biologists, partly as a way to move them away
> > > from
> > > being
> > > nothing more than taxonomists.  In order for biology to gain the
> > > scientific
> > > stature of chemistry and physics they needed to do more experiments,
> > > create
> > > more theories, and do more experiments to substantiate the theories.
> >
> > This certainly jibes with what I have observed in the literature.
> > Biologists do seem to embrace it more.
>
> One thing that biology students would probably appreciate is a good
> demo of "phase imaging." Here is an idea that I have never tried.
>
> Suppose a laser beam is expended (with two lenses) to a diameter of
> about 1 cm^2. Then it is split into two beams, like in an
> interferometer, and recombined into one beam projected into a screen.
> Suppose a small piece of glass (a microscopic slide) or plastic is
> partially covered with a transparent foil of thin plastic (mylar).
> Placing this transparent object into one of the beams would probably
> create a contrast (for example, mylar-coated area being darker or
> brighter that the other area. Stretching the film (reduction of
> thickness) would probably change the contrast.
>
> Have someone tried such demonstration? Biologists often use phase
> microscopy without understanding it. Such demo, if it works, would
> probably by appreciated by many.  This idea, by the way, came to me in
> a dream, last night.
>
>
> - - - - - - - - - - - - - -
> Ludwik Kowalski, a retired physics teacher and an amateur journalist.
> Updated links  to publications and reviews are at:
>
> http://csam.montclair.edu/~kowalski/cf/   http://csam.montclair.edu/~kowalski/my_opeds.html
>    http://csam.montclair.edu/~kowalski/revcom.html
>
> Also an ESSAY ON ECONOMICS at: http://csam.montclair.edu/~kowalski/economy/essay9.html
>
>
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- - - - - - - - - - - - - -
Ludwik Kowalski, a retired physics teacher and an amateur journalist.  
Updated links  to publications and reviews are at:

http://csam.montclair.edu/~kowalski/cf/   http://csam.montclair.edu/~kowalski/my_opeds.html 
   http://csam.montclair.edu/~kowalski/revcom.html

Also an ESSAY ON ECONOMICS at: http://csam.montclair.edu/~kowalski/economy/essay9.html