why is a coverslip used
Answers
A microscope slide is a thin sheet of glass used to hold objects for examination under a microscope. A standard microscope slide (shown on the right) is 75 x 25 mm (3" X 1") and 1.2 mm thick. A range of other sizes is available for various special purposes.
Since compound or high power microscopes have a very narrow region within which they focus, the object to be viewed ("specimen") should typically be placed on the middle of the slide with another, much thinner square (or circle or rectangle) of glass placed over the specimen. This smaller sheet of glass, called a cover slip or cover glass, is usually between 18 and 25 mm on a side. The cover glass serves two purposes: (1) it protects the microscope's objective lens from contacting the specimen, and (2) it creates an even thickness (in wet mounts) for viewing.