ELECTRON MICROSCOPY (EM)

In EM, the object is viewed by a beam of electrons instead of visible light. An electron beam has a shorter wadelength (h = 0.004 nm) compared with visible light (h = 400 nm). Therefore, an EM has higher resalving power than LM. Till now electron microscopy is the best available method to study biological ultrastructure.

The resolving power of most modem EMS ranges between 100 pm to 0.1 nm. However, problems of specimen preparation, and radiation damage limit the resolution of biological objects to about 2 nm, even this is 100 times better than the resolution achieved by the best LMs. Further, the magnifying power of the EM is upto 200,000 X. The two types of EM are transmission electron microscope (TEM) and scanning electron microscope (SEM). about which you will study in the following section.