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how do you determine the total magnification of a microscope

how do you determine the total magnification of a microscope


Total magnification is determined by multiplying the magnification of the ocular

You multiply the magnification of the eyepiece by the multiplication of the lens you’re using.So for example, if the eyepiece is 10x, and the lens is 40x, that will create a magnification of 400x.The magnification of the objective time the magnification of the eyepiece is the simple answer. That has to be multiplied by the addition of any inserts that change the magnification such as an Otivar* or polarized light analyzer that changes the tube length or has optics that modify the effective tube length.For example a 10x eyepiece and 5x objective designed for a 160 mm tube that are only 100 mm apart will have a magnification about 10 X 5 X100/160 or 31.25x. If a 1.6x Optivar were added the magnification would be back to 50x.If you are working with a photograph you must allow for the protection and or optics involved there as well.In reality the only way to know for sure is to view something of a know size with an eyepiece that can can measure the size or measure in a photograph and calculate the overall magnification. That is due to there being slight variations in the magnification of objectives, eyepieces and all the other variables that you can’t know with certainty.With enough care the size of an object under a microscope can be measured to very close tolerances. The closer the tolerances the harder the job.

the total magnification is the magnification of the objective (10x/40x/100x usually, but can be something else) which is further magnified by the eye piece (typically 10x, but others exist).

How to Calculate Total Magnification

Most compound microscopes have a 10x eyepiece and three objectives, 4x, 10x and 40x. Others also have a 100x magnification power. Therefore, the least total magnification of an image is 40x and the highest is 1000x. In order to view a specimen clearly under the microscope, begin with the lowest power objective (4x) to focus on the specimen, then use higher objective lenses (10x to 100x) to get a closer view of the image.


Telescopes and microscopes typically use two lenses. The user looks through the ocular lens, or eye piece, while an objective lens on the opposite end of the device further magnifies the object under observation. Though the two devices work similarly, the process for calculating their magnification is different.

Magnification in Microscopes

The formula for the total magnification of a microscope is the objective lens magnification times the ocular lens magnification. Almost all adjustable microscopes have the magnification of each lens written on the side of the lens. If you can’t find it, look in the user’s manual for the figures. Most microscopes have an ocular lens magnification of 10. In a microscope with an ocular magnification of 10 and an objective magnification of 20, the total magnification would be 200x.

Magnification in Telescopes

The formula for total magnification of a telescope is the focal length of the objective lens divided by the focal length of the eyepiece lens. The focal length is the distance between the center of the lens and the point where it is in focus. As with microscopes, you can find this data in the owner’s manual or on the labeling of the specific device. In a telescope with an objective lens focal length of 1000 mm and an eyepiece focal length of 10mm, the total magnification would be 100x.

How to Determine Magnification of a Microscope


The magnification of a microscope describes the increase in apparent size of an object compared with its actual size. An object magnified 10 times (10X) appears 10 times larger than it really is. Total magnification is the product of the ocular lens magnification and the objective lens magnification. Magnification does not describe the quality of the image. Magnifying an object without good resolution is called empty magnification, as the image appears larger but no greater detail can be seen. Resolution typically limits the usefulness of light microscopes rather than magnification.

Record the magnification of the ocular lens in the eyepiece. The magnification of the ocular lens is typically engraved on the side of the eyepiece.

Record the magnification of the objective lens. The magnification is frequently engraved along with the numerical aperture (NA) on the side of the objective lens. Many compound light microscopes allow different objective lenses to be rotated into use on the nosepiece. Each objective lens has a different magnification.

Multiply the magnification of the eyepiece by the magnification of the objective lens to produce total magnification. For example, a 10X ocular lens and a 40X objective lens will produce a total magnification of 400X (10 x 40 = 400). Changing the ocular lens or objective lens to lenses with a different magnification will change the total magnification of the microscope. Usually, it is the objective lens that is changed to increase or decrease magnification.


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