Question

Explain what the diffraction limit is and how it is connected to the spatial resolution of an optical system. Is it possible to resolve features smaller than the diffraction limit? Can you resolve 100 nm features using an optical microscope? How about 100 pm?

Answer 1

When lens is used in an optical instrument and the lens is well corrected for abberations,The light rays must be focused at one point. But, due to diffraction the light is focused into a finite area. It can be discussed as a plane wave incident on a convex lens after passing through a circular apperature. A diffraction pattern is formed and the central maxima has a radius of where f is focal length and a is the diameter of apperature and v is the image distance. objects that form an image closer than this will not be resolved

corressponding min. seperation between objects= here m is magnification of microscope

for general microscope has magnifiaction of 1000

and wavelength be 500 nm and v = 0.1 m

we get the limit as 2.4 nm

so objects with seperation of 2.4 nm cannot be viewed

so we can resolve features in the range of 100 nm but not 100 pm