
173Nanosensor Laboratory
the shortest distance between two points on a specimen that can be distin-
guished by the observer or camera system as separate entities. The Numerical
Aperture of a lens (a number that expresses the ability of a lens to resolve ne
detail in an object being observed) is
NA = nsin θ (3.29)
where
n is the refractive index of the working medium
θ is the half-angle of the maximum cone of light that can enter or exit the
lens
Diffraction is the change in the directions and intensities of a group of
waves after passing by an obstacle or through an aperture whose size is
approximately the same as the wavelength of ...