The invisible enemy?
Would it be possible to view and detect SARS-CoV-2 using a conventional optical microscope? This corona virus has dimensions between 70 - 90 nm for a single virion particle.
With an optical microscope, conventional wisdom states that objects smaller than about 200 nm cannot be seen because of a restriction known as the "diffraction limit". At these dimensions, a transmission microscope (light coming from beneath a microscope slide) is unable to cast a sharp outline to the eyepiece due to bending of visible light around the object's outside edges. Two light rays travelling either side of such a small target would be diffracted and become merged together before they reached the first object lens - therefore no shadow image cast.
However, I came across a published article recently that may have a solution. This article was written in 2011, some nine years ago, and it uses tiny 200 um sized glass spheres to increase resolution beyond the diffraction limit...
https://www.cnet.com/news/nanoscope-makes-live-viruses-visible-for-first-time/.
With this idea, the glass sphere is located almost in contact with the target object to be viewed. So light enters the sphere at a distance much less than the wavelength of light. It therefore picks up the "near-field" radiation, known as evanescent waves, which are not diffracted in the same way as "far-field" radiation. These evanescent waves contain a lot of the spacial high frequency content normally lost to a conventional microscope. That spacial high frequency is in effect the width distance of the target object in a form of "Fourier Transform" principle.
The claim is that this new technique can resolve width distances down to at least 50 nm, which should be more than ample to see the virion particle. It will not necessarily let you identify the type of virus, or indeed if it is a virus at all. But it will allow you to know that there is "something" of that dimension present in the sample you are looking at. If the sample was, say, saliva taken from a suspected asymptomatic person, then the presence of tiny particles of around 70/90 nm dimensions would be sufficient to trigger a more rigorous PCR test to confirm or otherwise whether the person involved is infected with COVID-19. It could do this very early on in the disease development phase and thereby reduce the chances of this person becoming a super spreader. It might also allow this person to be diagnosed before the disease takes full hold on invading further organs in the body - thereby saving their life.