How a Microscope Works

Microscopes are tools used to look at objects too small or detailed to be seen by the human eye. “Micro” means small and “scope” means to look at for the purpose of evaluation, and a microscope does just that, using light and magnifying glasses.

The first clear description of how a magnifying glass works appeared in the Book of Optics, written by the Arab scientist Ibn al-Haytham in the 11th century. This work later influenced discoveries and inventions throughout Europe, from the creation of eye spectacles in Italy during the 12th century to the compound microscope’s invention by Hans and Zacharias Jansen in 1595 and the prolific microscope advancements of “the father of microscopy,” Dutch scientist Anton van Leeuwenhoek.

But how does a microscope work? Basically, light shines through an object to make it bigger so the human eye can see it. A microscope uses lenses to enlarge objects. Objects being enlarged must allow light to pass through and illuminate them. Some microscopes use different containers and liquids to give objects better definition or clarity. Light shines up through the tray and that light is enlarged through the lenses for the viewer.

A lens can be made out of glass or plastic. Lenses come in a variety of forms, and most lenses are either concave (indented) or convex (bulging out) in form. Their shape allows them to redirect light as it passes through them. Light passes through a lens and is changed, then focused. This happens in many things, from eyeglasses to raindrops on a window. In a microscope, the lens amplifies an object so that the viewer can see details.

The most basic and ubiquitous version of a microscope is an optical microscope. These are the microscopes you see in high school biology classrooms and science project Christmas gifts. This microscope uses lenses and light to enlarge an object for viewing by the naked human eye. There are two types: simple (one lens) and compound (multiple lenses). Optical aberrations, including differences in color refraction make an image blurry to the viewer. The more lenses used, the more image clarity.

From bottom to top, there are four main components of a standard optical microscope. There is a light source, usually a bulb, at the base of the microscope. Above the light is a transparent tray where the object being viewed rests. Above the tray is a tube containing one or more lenses. The lens at the tube’s base is called the objective lens. Above the objective lens(es) are eyepiece lenses the viewer looks through at an image.

There are other types of microscopes for many uses, but this is the most common. For example, an electron microscope can look at the cellular structures of object by bending electrons with magnets much the same way that an optical microscope bends light with glass. Some microscopes even use x-rays.

Microscopes work because people have used science to examine, learn about, and then manipulate the nature around us. In turn, microscopes allow all of us a way to investigate and better understand the world around us.