Can viruses be seen under a light microscope?
Can't see the virus.
The explanation is as follows:
Because the virus is small. The diameter of most single virus particles is about 100nm, that is to say, it is possible to barely see it with the naked eye only by arranging about 100,000 virus particles.
Viruses are so tiny that most viruses can only be observed with the aid of an electron microscope, which has a resolution 1,000 times that of a light microscope. The size of different viruses varies greatly. The smallest (Geminiviruses) such as plants are only 18-20nm in diameter, the largest animal poxviruses (Poxviruses) are 300-450nm × 170-260nm in size, and the longest such as Filoviridae (Filoviridae) The size of the virus particle is 80nm×790-14000nm.
The resolution distance of the optical microscope is d=0.61λ/NA where
d—the resolving distance of the objective lens, in nm.
λ——the wavelength of illumination light, in nm.
NA - the numerical aperture of the objective lens
For example, the numerical aperture of the oil immersion objective is 1.25, the visible light wavelength range is 400-700nm, and the average wavelength is 550 nm, then d=270 nm, which is about half the wavelength of the illumination light. Generally, the limit of the resolving power of a microscope illuminated by visible light is 0.2 μm or 200 nm, which is larger than the diameter of the virus, so the virus cannot be seen with an optical microscope.
Bacteria are much larger than viruses. The diameter of a single coccus is about 0.8 to 1.2 μm. Most bacilli are medium in size, 2 to 5 μm in length and 0.3 to 1 μm in width, within the observable range of an optical microscope.
