Question

Why is a mirror fixed on a microscope?

Answer 1

not all microscopes have a mirror , some have a light bulb instead , however the principals are the same ,both are designed to provide light to the object that is being studied , in the case of the ones fitted with a mirror ,the mirror can be tilted to catch the sunlight and directed upon your selected sample for observation, likewise so can a bulb which can either be battery or mains operated usually through a transformer for safety