What is the total magnification of a microscope with an eyepiece of 10X and an objective of 60x?

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A microscope's total magnification is a combination of the eyepieces and the objective lens. For example, a biological microscope with 10x eyepieces and a 40x objective has 400x magnification. There are however, a few limits to the amount of total magnification that can be reached before empty magnification comes into play. Empty magnification occurs when the image continues to be enlarged, but no additional detail is resolved. This is often the case when higher magnification eyepieces are used. In order to avoid empty magnification, there are a few simple steps that are helpful to follow.

Eyepiece and Objective Combinations for Optimal Magnification

When selecting a combination of eyepieces and objective lenses for the optimal magnification, without ending up with "empty magnification" it is important to consider the numerical aperature (NA) of the objective. The numerical aperture of a microscope objective defines the objective's resolution. Each microscope objective has a minimum and maximum magnification necessary for the details in an image to be resolved. A simple formula for the minimum value is (500 x NA). And for the maximum magnification (1000 x NA). Magnifications higher than this value will result in empty magnification, or an image that has a poor resolution. The table below shows some typical NA values with their corresponding objective and provides a range of useful magnification combinations. The blank boxes in the table would provide empty magnification and should be avoided. For example, pairing 20x eyepieces with a 100x objective would not provide good resolution and would result in empty magnification. To determine this, we took 1.25NA x 1000 = 1250 magnification maximum. However, the combination of the 100x objective x 20x eyepieces = 2000, which is above the maximum magnification.

Range of Useful Magnification based on NA of Objectives

If you have any questions about your microscope's magnification, contact Microscope World.

Magnification:

Figuring Total Magnification

Magnifying Objects/ Focusing Image:

When viewing a slide through the microscope make sure that the stage is all the way down and the 4X scanning objective is locked into place. Place the slide that you want to view over the aperture and gently move the stage clips over top of the slide to hold it into place. Beginning with the 4X objective, looking through the eyepiece making sure to keep both eyes open (if you have trouble cover one eye with your hand) slowly move the stage upward using the coarse adjustment knob until the image becomes clear. This is the only time in the process that you will need to use the coarse adjustment knob. The microscopes that you will be using are parfocal, meaning that the image does not need to be radically focused when changing the magnification. To magnify the image to the next level rotate the nosepiece to the 10X objective. While looking through the eyepiece focus the image into view using only the fine adjustment knob, this should only take a slight turn of the fine adjustment knob to complete this task. To magnify the image to the next level rotate the nosepiece to the 40X objective. While looking through the eyepiece focus the image into view using only the fine adjustment knob, this should only take a slight turn of the fine adjustment knob to complete this task.

Total Magnification:

To figure the total magnification of an image that you are viewing through the microscope is really quite simple. To get the total magnification take the power of the objective (4X, 10X, 40x) and multiply by the power of the eyepiece, usually 10X.

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This entry was posted on March 16, 2020 by Accu-Scope.

Most compound microscopes come with interchangeable lenses known as objective lenses. Objective lenses come in various magnification powers, with the most common being 4x, 10x, 40x, and 100x, also known as scanning, low power, high power, and (typically) oil immersion objectives, respectively. Let’s take a closer look at each of the different magnifications of objective lenses and when you would use them.

Scanning Objective Lens (4x)

A scanning objective lens provides the lowest magnification power of all objective lenses. 4x is a common magnification for scanning objectives and, when combined with the magnification power of a 10x eyepiece lens, a 4x scanning objective lens gives a total magnification of 40x. The name “scanning” objective lens comes from the fact that they provide observers with about enough magnification for a good overview of the slide, essentially a “scan” of the slide. Some objectives with even lower power are discussed in Specialty Objectives below.

Low Power Objective (10x)

The low power objective lens has more magnification power than the scanning objective lens, and it is one of the most helpful lenses when it comes to observing and analyzing glass slide samples. The total magnification of a low power objective lens combined with a 10x eyepiece lens is 100x magnification, giving you a closer view of the slide than a scanning objective lens without getting too close for general viewing purposes.

High Power Objective Lens (40x)

The high-powered objective lens (also called “high dry” lens) is ideal for observing fine details within a specimen sample. The total magnification of a high-power objective lens combined with a 10x eyepiece is equal to 400x magnification, giving you a very detailed picture of the specimen in your slide.

Oil Immersion Objective Lens (100x)

The oil immersion objective lens provides the most powerful magnification, with a whopping magnification total of 1000x when combined with a 10x eyepiece. But the refractive index of air and your glass slide are slightly different, so a special immersion oil must be used to help bridge the gap. Without adding a drop of immersion oil, the oil immersion objective lens will not function correctly, the specimen will appear blurry, and you will not achieve an ideal magnification or resolution. Oil immersion lenses are also available from some manufacturers in lower magnifications, and provide higher resolution than their "high dry" counterparts.

Specialty Objective Lenses (2x, 50x Oil, 60x and 100x Dry)

There are several other objective lens magnifications available with utility for particular applications. The 2x objective, widely used in pathology, has only ½ the magnification of a 4x scanning lens, thus providing a better overview of the sample on the slide. The 50x oil immersion objective, often used in place of the 40x objective, is used as a gold standard for observing blood smears. The 60x objective, often available in either dry or oil immersion, provides 50% greater magnification than a 40x lens. The 60x dry is sometimes chosen over a 100x oil immersion lens for higher magnification without the need to use immersion oil.  Finally the 100x dry objective doesn’t need immersion oil to deliver high magnification (still 1000x when combined with 10x eyepieces). However, the numerical aperture (an indication of resolving power of an objective) of a 100x dry objective is much lower than that of a 100x oil immersion objective and, as a result, the ability of the lens to resolve fine details in the specimen is much lower, too.

It is important to always use the correct immersion media (e.g. air, water, oil, etc.) that is specified by your objective lens.

• The image produced by the wrong immersion media will be blurry. In general, objectives are engineered to "look" through an immersion medium with a particular refractive index (a topic for another article). For example, air has a refractive index of close to 1.0, whereas standard immersion oil has a refractive index of ~1.51.
• You can damage the objective if you use the wrong immersion oil.

If you are interested in buying various types of objective lenses for your microscope in the classroom, laboratory, research facility, or any other purpose, ACCU-SCOPE can provide the products you are looking for. Contact us today to learn more about our objective lenses and other microscope accessories.