Final answer:
A crime scene investigator can use forensic lamps to find particles on a carpet, often with the assistance of alternate light sources for fluorescence. For more detail, microscopic methods involving monochromators and spectral analyzers might be used to analyze the particle's molecular fingerprints.
Step-by-step explanation:
A crime scene investigator may utilize a number of sophisticated techniques to find particle evidence on a carpet at a crime scene. One common method is the use of forensic lamps, also known as alternate light sources (ALS), which can make certain substances visible to the eye due to their fluorescent properties when exposed to specific wavelengths of light. However, for a more detailed analysis, the investigator might use microscopic techniques that can provide insight into the chemical composition of the particles. Such techniques include the use of microscopes attached to monochromators and spectral analyzers that detect scattered light from particles after being hit by a monochromatic light, such as from a laser. This scattered light can reveal molecular fingerprints of the substances on the carpet, potentially relating them to suspects or the crime scene.