Final answer:
An electron microscope is necessary to see viruses, which are too small to be resolved by standard light microscopy. Viruses range in size from about 20 to hundreds of nanometers, significantly smaller than bacteria, fungi, and protozoa, all of which can be seen with light microscopes to varying extents.
Step-by-step explanation:
It is necessary to use an electron microscope to see viruses. Viruses are much smaller than bacteria, fungi, and protozoa, with sizes ranging from about 20 nanometers to hundreds of nanometers. Most bacteria measure around 1 micrometer in size, and they can be viewed using light microscopy. However, viruses, which are about 10 times smaller than bacteria, cannot be resolved with standard light microscopes and require the much higher magnification and resolving power of electron microscopes.
Electron microscopes, such as the transmission electron microscope (TEM) and scanning electron microscope (SEM), are essential tools for visualizing viruses. These microscopes work by using a beam of electrons to create an image of a specimen, allowing researchers to view objects at the nanometer scale. Since viruses lack the necessary contrast to be seen under a standard light microscope and are smaller than the wavelength of visible light, an electron microscope is required to view them.
For instance, the size of a typical virus is very small relative to the size of cells and organelles and usually measures about 100 nm. This is significantly below the resolution limit of conventional light microscopy, but within the capabilities of an electron microscope, enabling the detailed study of virus structure and aiding the understanding of viral infections and diseases.