Dimensions and Magnification
An atomic force microscope is optimized for measuring surface features that are
extremely small, thus it is important to be familiar with the dimensions of the
features being measured. An atomic force microscope is capable of imaging features
as small as a carbon atom and as large as the cross section of a human hair. A
carbon atom is approximately .25 nanometers (nm) in diameter and the diameter of
a human hair is approximately 80 microns (чm) in diameter.
The common unit of dimension used for making measurements in an atomic force
microscope is the nanometer. A nanometer is one billionth of a meter:
1 meter = 1,000,000,000 nanometers
1 micron = 1,000 nanometers
Another common unit of measure is the Angstrom. There are ten angstroms (Е) in one
nanometer:
1 nanometer = 10 Angstroms
Magnification in an atomic force microscope is the ratio of the actual size of a
feature to the size of the feature when viewed on a computer screen. Thus when an
entire cross section of a human hair is viewed on a 500 MM computer monitor (20
inch monitor) the magnification is:
Magnification = 500 mm/.08 mm = 6,250 X
In the case of extremely high resolution imaging, the entire field of view of the
image may be 100 nanometers. In this case the magnification on a 500 mm computer
screen is:
Magnification = 500 mm/(100 nm*1 mm/1,000,000 nm)=5,000,000 X
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