Microscopes - optical instruments repairedThe standard monocular microscope has at least two magnifying lenses, with a light reflecting mirror fixed below the glass slide which holds the specimen. The focusing screws on the side of the instrument adjust the lenses to give a sharp and clear picture of the specimen.

Just a small microscope can magnify an object 100 times, so a hair of 0.1 mm thickness would look 1 cm thick. A good light microscope can magnify clearly to about 2000 times. The specimen being viewed, however, must be thin or reasonably flat, as light passes through it, from the reflecting mirror below, and up into the objective lens, which magnifies the image. This image is then magnified again by the eyepiece lens, and is then viewed by the observer.

Better quality microscopes have differently powered objective lenses, that can be swung into position when required. The electron microscope is far more powerful, and is used for specimens which are so small that they can't be seen by an ordinary microscope. They can see up to about a million times!