What is a light microscope? (with photos)

An optical microscope.

A light microscope, also called an optical microscope, is an instrument for observing small objects using visible light and lenses. It is a widely used and recognized microscope in the scientific community. The device can be used to visualize live or dead samples and can maximize those samples up to a thousand times (1000x) their actual size. Light microscopes include almost all compound and stereo microscopes.

A basic light microscope.

This type of microscope consists of an objective lens, an eyepiece lens, a stage, a light source, a condenser, a tube, an arm to support the tube and a focusing system. The specimen is placed on the stage, a platform usually equipped with metal arms to hold the specimen or blade in place. The lamp is located below the stage, so that the light illuminates the specimen. The tube focuses the stage so that the eyepiece lens, or eyepiece, is at the end of the tube and the objective lens is at the end closest to the sample.

A woman using an optical microscope.

The objective lens is a small piece of round glass that collects light from a small area of ​​the specimen at a short focal length and directs the light into the tube. The image is then magnified by the eyepiece lens, which is placed in the eye. As the objective lens is convex, it focuses and directs light towards its center. In contrast, the concave shape of the eyepiece lens serves to scatter light as it strikes the eye, making the image larger. The condenser is a lens, usually implanted on the stage or located just below it, that condenses the light rays from the light source at the point being examined in the sample above.

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Three paramecia are seen under the microscope.

A simple light microscope uses only one magnifying glass, but today, most microscopes use two or more lenses to magnify the image. Most microscopes today are compound microscopes that use more than one magnifying glass. The eyepiece typically magnifies to 2x, 4x, or 10x actual size and the eyepiece lens can magnify 4x, 5x, 10x, 20x, 40x, 50x, and 100x. A microscope usually comes with three eyepiece lenses of different magnification levels placed on a rotating revolving nosepiece. There may also be a fourth lens used for viewing oil immersion specimens, where a drop of oil is placed on the slide to further refract the light and the oil immersion lens is lowered until it touches the drop of oil.

In 1610, Galileo Galilei unveiled his version of the compound microscope.

The relationship of glass to magnification and the concept of lenses were discovered by the Romans in the first century. AD lenses were eventually used in the late 1200s as eyeglasses. This may have set the stage for Zaccharias and Hans Jannsen, Dutch eyeglass makers who, in the 1590s, would have invented the first compound microscope by experimenting with multiple lenses in a tube. The validity of the Jannsens’ claim to this invention, however, is highly contested. Many historians attribute the development of the compound microscope and technologically similar telescopes to the Tuscan scientist Galileo Galilei in the early 18th century.

Microscopes typically use two or more lenses to magnify objects.

Later, a Dutch shop apprentice named Anton Von Leeuwenhoek refined lens making to achieve a steep curvature in a small lens, allowing him to focus on much smaller specimens than ever before. He is often referred to as the father of microscopy, as he introduced the microscope as a vital instrument to the field of biology. In addition to other discoveries, Anton Von Leeuwenhoek was the first to see bacteria, yeast and organisms in a drop of water.

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