Читать книгу Cell Biology - Stephen R. Bolsover - Страница 26

Whereas the image in a transmission electron microscope is formed by electrons transmitted through the specimen, in the scanning electron microscope it is formed from electrons that are reflected back from the surface of a specimen as the electron beam scans rapidly back and forth over it. These reflected electrons are detected and used to generate a picture on a display monitor. The scanning electron microscope operates over a wide magnification range, from 10 times to 100 000 times, and has a wide depth of focus. The images created give an excellent impression of the three‐dimensional shape of objects (Figure 1.7). The scanning electron microscope is therefore particularly useful for providing topographical information on the surfaces of cells or tissues. Modern instruments have a resolution of about 1 nm.