Abbe limit

The Abbe limit, also known as the diffraction limit, is a fundamental concept in physics that describes the resolution limit of optical instruments like microscopes. In 1873, physicist Ernst Abbe developed a theory explaining that the ability to resolve fine details is limited by the wavelength of light used and the numerical aperture (N.A.) of the objective lens.

Essentially, smaller details produce wider diffraction angles. An objective lens can only collect diffracted light within its N.A. If the N.A. is too low, finer details of an object will not be resolved, regardless of magnification. This principle dictates the smallest feature size that can be distinguished, a crucial factor in microscopy and other optical technologies.12