Microscope CalculationsMATH + SCIENCE = FUN

How to Calculate Total Magnification To calculate the total magnification

of a compound microscope, you

must multiply the magnification of

the ocular lens (lens in the

eyepiece) by the magnification of

the objective lens.

Total Magnification Formula Total Mag = Mag(ocular lens) x Mag(objective

lens)

Total Magnification

What would the magnification of a microscope with the ocular lens that enlarges the image by 10x and an objective lens that enlarges the image by 10x(medium power)?

Total Mag = Mag(ocular lens) x Mag(objective lens)

=10 x 10

=100x

• Therefore the magnification with an ocular lens of 10x and an objective lens of 10x is 100x.

Total Magnification What about for microscopes with an ocular lens of 10x

and objective lenses of:

4x (low power)

40x (high power)

What lenses would you combine if you wanted to magnify an object:

100x

400x

Measuring the Field of View Field of View (FOV) – The diameter of the

circle of light that you see when looking into a microscope.

As the power gets greater, the field of view gets smaller.

Try measuring the FOV on low power

by using your agenda ruler.

The field of view on low power is

4mm.

Calculating FOV for Medium & High Power It is very difficult to measure the FOV under medium and high

power lenses since the magnification is so high. However, you can use formulas to calculate them.

Field of View Formulas

Try calculating the medium and high FOV when the low FOV is 4mm.

Calculating FOV for Medium & High Power

= 1.6 mm or 1600µm

= 0.4 mm or 400µm

Estimating size of microscope objects Using what you know about FOV calculations, you can now

estimate the size of your specimen.

Estimating Size Formula

FOV can represent low, medium, or high power. Number of specimens represents the number that can fit across the FOV diameter.

What if 4 of your specimens could fit into the field of view? What would be the estimated size of the original specimen?

Formula ReviewTotal Magnification

Total Mag = Mag(ocular lens) x Mag(objective lens)

Field of View Diameter (Length)

Low FOV – Can be measured using a ruler

under the low-power lens.

Estimated Size of Specimen