What is the primary function of a scanning electron microscope (SEM)?

The primary function of a scanning electron microscope (SEM) is indeed to pass a focused electron beam over surfaces. This technique allows for the generation of high-resolution, three-dimensional images of the sample surface. The electrons interact with the atoms in the sample, producing various signals that can be used to form detailed images, revealing the surface topography and other relevant features at a microscale.

By operating in this manner, SEM provides insights into the physical and topographical characteristics of a sample, making it particularly valuable in forensic analysis, materials science, and biology. Compared to techniques that utilize light for imaging, SEM can achieve much higher magnifications and resolutions, which is crucial for examining fine details that would otherwise be invisible with optical microscopy.

The other options do not accurately capture the specific function of SEM. Magnifying visual evidence typically refers to more general optical microscopy methods, while creating images with light is characteristic of light microscopy techniques. Analyzing chemical compositions, though important, is primarily the role of other types of microscopes or spectroscopy methods, rather than the SEM's primary function.