Final answer:
Phase Contrast Microscopy enhances contrast in transparent specimens by using phase shifts in light caused by different refractive indices, allowing the observation of live, unfixed, and unstained cells and their structures.
Step-by-step explanation:
Phase Contrast Microscopy is a technique used to enhance the contrast of transparent specimens without the need for staining. It utilizes the principle of phase contrast, where light passing through different parts of the specimen is shifted in phase. This phase shift occurs due to variations in refractive index within the specimen, such as between cell organelles and the surrounding cytoplasm. The optics of the phase-contrast microscope are designed to convert these phase shifts into variations in intensity, resulting in an image with higher contrast. This allows for the live, unfixed, and unstained cells to be observed, making the phase-contrast microscope a cost-effective and valuable tool for examining cellular structures like organelles and endospores.