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Optical Microscope Limits
Name: Mellom
Status: Other
Grade: Other
Location: N/A
Country: N/A
Date: September 2005
Question:
Why is it not possible to obtain infinite magnification
by using lenses with greater magnifying power?
Replies:
When the wavelength of the radiation used in the microscope (be it
infrared, visible, ultraviolet, x-rays or even particle waves like
electrons or neutrons) becomes the same order of magnitude as the sample
(or the optical surfaces of the instrument) light begins to diffract, that
is it scatters in directions other than the "line of sight" of the
detecting radiation. This limits the distinctness of the boundaries of the
object or the image being processed by the instrument. There are
techniques -- too involved to address here -- where this limitation can be
minimized, but it becomes an ongoing uphill battle. If you search the
term: "microscope diffraction limits" on Google you will find both the
cause of the classical limit as well as various techniques for extending
the range of magnification and resolution of various instruments and techniques.
Vince Calder
Unfortunately, photons (light particles) do not move in a perfectly straight
line. They oscillate along their line of movement. (kind of like a car
swerving as it travels down the road) If you lined up enough lenses
to be able to see at that scale, you would still not see your image,
because all
of the photons would be oscillating as they reach the lens. Only as the
magnification is further reduced can the image become clearer, since
whatever you are looking at is now many times the size of a photon's
oscillation.
There are other microscopes, however, that do not use light to view very
small items. An electron microscope uses a stream of electrons, and can
'see' right down to an atomic scale.
Ryan Belscamper
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Update: June 2012
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