They generally do not magnify as much as compound microscopes around 40xx maximum but give a truly stereoscopic view. The metal is able to reflect the electrons. They are also much more expensive than light microscopes.
Though this is a significant amount of magnification, it is dwarfed by the electron microscope's ability to achieve a magnification of up to ,x.
Tungsten filament is used to produce electrons. Electron microscopes, which provide much more detail and magnification at a greater price, are used in high-end research facilities and laboratories.
This is a physical limit imposed by the wavelength of the light. It has low resolving power 0.