Explain the Phase Contrast Microscop?

Unpigmented and unstained living cells can be easily observed by phase contrast microscope. It has a special objective and a condenser that converts slight differences in refractive index and cell density into easily detected variations in light intensity and produce visible image of the structure under study. The image appears dark against a light background. Phase contrast microscopy is used widely to study microbial motility, determining the shape of living cells and detecting microbial structures like inclusion bodies and endospores etc.