Indeed.
I cover numerical aperture and resolution in my microscope book.
An unstained nucleus in a microbe might be as transparent as the
cytoplasm around it, rendering it invisible even with the best objectives
and condensers. But phase contrast will make it show up, since it has
a different refractive index than the cytoplasm. The same goes for
differential interference contrast.
So if you are viewing live critters that you can't or don't want to stain,
you might pay the extra $600 for phase contrast.
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Get a free science project every week! "http://scitoys.com/newsletter.html"On Tue, Feb 28, 2012 at 3:58 PM, Cory Tobin <cory.tobin@gmail.com> wrote:
If you have a choice go with a higher numerical aperture rather than a
higher magnification. High mag doesn't get you any extra information,
it just makes the image appear larger. If you have high magnification
and low NA you'll just end up with a really large, blurry image.
In addition to Simon's advice that scopes without condensers are toys,
I would add that if the scope comes with an objective and they don't
specify* the NA of the objective, just the magnification, it's
_probably_ a toy. If they don't tell you the NA, it's probably
ridiculously low. The manufacturers of toy microscopes like to
advertise stupidly large magnifications, which doesn't tell you
anything about how small it will resolve.
* Sometimes the NA is specified in parentheses next to the
magnification. 60x (0.9) would mean 60 times magnification with a
numerical aperture of 0.9.
-cory
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