An electron microscope uses a beam of high-energy electrons instead of visible light to produce highly magnified images. Because electrons have a much shorter wavelength than light, the resolving power is far greater — up to several million times magnification.
Based on de Broglie's theory, electrons exhibit wave-like properties. When accelerated at high voltage, their wavelength becomes extremely small — much shorter than visible light. This short wavelength provides very high resolution, enabling visualization of structures at the nanometer scale.
Contains a heated tungsten filament or field emission source that emits electrons. These are accelerated by high voltage (up to 300 kV) to form a high-speed beam.
Replace glass lenses of light microscopes. Use magnetic fields to focus the electron beam. Includes condenser lens, objective lens, and projector lens.
Holds the specimen under high vacuum to prevent electron scattering by air molecules. The entire column is evacuated.
Includes fluorescent screen, photographic plate, or digital camera that converts the electron image into visible form. Modern systems display on computer monitors.
Secondary electron detector captures electrons emitted from the specimen surface (SEM). Backscattered electron detector captures electrons reflected back, providing compositional contrast.
In a Scanning Electron Microscope, the focused beam scans across the specimen surface. Secondary electrons are emitted and collected by detectors to build a 3D surface image point by point. Provides excellent depth of field.
In a Transmission Electron Microscope, electrons pass through an ultra-thin specimen. Denser areas scatter more electrons and appear darker. The transmitted beam is magnified by objective and projector lenses to form a 2D projection image.
1. Electron gun emits electrons
2. High voltage accelerates the beam
3. Condenser lens focuses the beam
4. Beam interacts with specimen
5. Detectors capture signals
6. Image displayed on screen
Study cell organelles, viruses, bacteria, tissue ultrastructure. Assists in disease diagnosis, cancer research, and biopsy examination.
Study metals, crystals, alloys, and nanomaterials. Analyze grain boundaries, defects, and surface morphology.
Analyze gunshot residues, fibers, and trace evidence with extreme detail.
Examine microchips, semiconductor devices, and circuit patterns at nanoscale resolution.