Final answer:
When viewing unstained material, more light is typically required than for stained preparations. Stains provide contrast, making specimen details more visible, whereas techniques like darkfield and phase-contrast microscopy improve visibility for unstained samples.
Step-by-step explanation:
When viewing unstained material using a microscope, more light is typically required compared to viewing a stained preparation. Stains and dyes enhance the contrast between cellular components and the background, making details more visible. Without stains, darkfield microscopy or other techniques like phase-contrast or polarized light microscopy can improve the visibility of transparent or low-contrast specimens. Fluorescence microscopy involves the use of fluorescent dyes that emit light upon excitation, making targeted structures within the specimen highly visible against a dark background, which differs significantly from the sample preparation for standard light microscopy.
In light microscopy, stains are crucial as they kill the cells but provide the necessary contrast to distinguish structures within the cells. For unstained live specimens, adjusting the contrast with special microscopy techniques becomes essential to properly identify features. Stained specimens are easier to observe under a light microscope because the colors added by the stain increase the contrast and visibility of the specimen's structure under the lens.