Why is a microscope used to observe bacteria? ?

A phase contrast microscope uses an optical technique that works by the use of a device to read the difference in thickness of the subject affecting the phasing of light resulting in a high contrast image. Staining bacteria also help microscope users to see bacterial structures that would have otherwise been invisible to the naked eye.

gravititional force is a force that is acting around you, it is non-contactable and it is a force that pulls you to the core of the earth.

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the answer is b ) square root of 5