Step 1: Differentiate between the main types of electron microscopy.
- Scanning Electron Microscopy (SEM): In SEM, a beam of electrons is scanned across the surface of a sample. Detectors collect secondary electrons, backscattered electrons, and X-rays emitted from the surface. This produces a high-resolution, 3D-like image of the sample's surface topography.
- Transmission Electron Microscopy (TEM): In TEM, a beam of electrons is transmitted through an ultra-thin slice of the sample. The electrons that pass through are focused to create an image. This provides extremely high magnification and resolution of the internal structure of the material, such as crystal structures, phases, and defects.
Step 2: Apply this to the question. Since TEM involves passing electrons through the material, it is used to study the internal structure. SEM is used for studying the surface (external) structure.
Conclusion: TEM is used for the study of the internal structure of fibrous materials.