The Basics of Microscope Magnification: Everything You Need to Know

In many disciplines, the microscope is a scientist’s best friend. It’s the trusty sidekick that provides insight, clarity and new perspectives as you dive into uncharted territory. We interact with microscopes so often that operating them can become sheer muscle memory, and we no longer think about why we use them as we do. In this article, we’ll take a step back to reacquaint ourselves with the basic tenets of microscope magnification

What Is Magnification?

Simply put, magnification refers to how much an object is visually enlarged when observed under a microscope. It’s usually represented in terms of x–for instance, 2x, 10x and 20x mean that the observable object appears to be twice as big, 10 times as big or 20 times as big when viewed through the microscope eyepiece. Like all things, even your microscope’s magnification has limits. Analog microscopes that use light and mirrors to magnify objects usually max out at about 1,500x magnification. This is because light wavelengths cause the image to appear unclear at that magnitude of magnification. Electron microscopes, however, can produce images that exhibit impressive clarity all the way up to 200,000x magnification since electrons have much shorter wavelengths. 

Measuring Magnification 

Most compound light microscopes have two types of lenses–the ocular lens and the objective lens. The ocular lens is the lens on the eyepiece. The objective lens is the lens closest to the object or slide being observed. Most microscopes have a rotating disc with at least three objective lenses attached, so the observer can choose an appropriate magnification. In order to measure the total magnification, you must calculate the product of the ocular lens and the objective lens. To do this, record the magnification of the ocular lens in the eyepiece and record the magnification of the objective lens (these numbers are usually engraved on the sides of both types of lenses). Next, multiply the ocular lens magnification by the objective lens magnification. This will give you the total magnification. For instance, if you are using an ocular lens with 10x magnification and an objective lens with 50x magnification, your total magnification is 500x. 

Adjusting Magnification

By switching up the configuration of your lenses, you can achieve a wide range of microscope magnification. A standard microscope eyepiece magnifies an object 10x. However, you can find eyepieces that magnify 15x, 20x and even 30x or higher. This presents a plethora of options in terms of combining the ocular and objective lenses to reach the perfect point of magnification. To adjust the magnification, simply switch out the ocular and/or the objective lenses until you find the ideal combination for viewing your sample or slide. Remember, the highest magnification is not always the best, as compound light microscopes can really only magnify up to a certain point before the images lose clarity and become unreliable.   

Things to Keep in Mind

Knowing how to measure and adjust your microscope are the building blocks for microscopy skills. But what other factors can affect how you view your sample? For starters, make sure the stage is all the way down and locked into place. The stage is the flat surface on which you rest your slide or sample for viewing. If it isn’t in a fixed position, you may have a hard time bringing your image into focus. When using the coarse adjustment knob to move the lenses up and down, or further away and closer to your objective, make sure you do not bring the lenses close enough to touch the slide. This could result in something as simple as bumping the slide and having to refocus, or as impactful as actually crushing your sample. As with any laboratory equipment, proceed carefully and with caution to prevent any unnecessary lab mishaps

Compound light microscopes are relatively easy-to-use machines, as long as you take care of them properly and understand the basics of magnification. Through the wide variety of ocular and objective lens combinations, you can visualize whole worlds in a slide, and maybe even make some surprising discoveries. Understanding the basics of microscope magnification can enable you to use this common piece of lab equipment to your best advantage.