The diffraction limit is an absolute limit in the size-scale for which we can resolve an image optically. In terms of a length scale $\Delta x,$ the diffraction limit is expressed as $\Delta x \geq \frac{\lambda}{4\pi}$ Since it is dependent on wavelength experimentally we find that we're limited in our resolution by available wavelengths. # Abbe limit In classical optical microscopy, the diffraction limit is often referred to as the _Abbe Diffraction limit_ or _Abbe limit._ Here in addition to the absolute diffraction limit, we are limited by the [[numerical aperture]] of our imaging device. # Photon diffraction limit We may also write the diffraction limit in terms of the [photon wave number](photon.md#wave-like%20properties). # In nano-optics The diffraction limit of photons approaching the visible spectrum is approximately where we draw the boundary between [optics](Optics%20(Index).md) and [nano-optics and nanophotonics](Nano-optics%20and%20nanophotonics%20(Index).md) since in the visible spectrum, the diffraction limit is on the order of a few hundred nanometers. ^7730cd ## Surpassing the diffraction limit ([... see more](Surpassing%20the%20diffraction%20limit.md)) #Electromagnetism/Optics/waveOptics/NanoOptics