Microscopes

Magnification, Field of View and Estimating Size

Eyepiece or Ocular Lens

Coarse Focus Knob

Fine Focus Knob

Arm

Stage Clips

Base

Revolving Nosepiece

High Power Objective Lens (40X)

Lower Power Objective Lens (10X)

Stage

Diaphragm

Light / Mirror

Body Tube

Magnification• Total magnification is how large the specimen appears under

the microscope

Total magnification = Eyepiece (ocular) x objective lens

Objective Lens Selected

Magnification of Objective Lens

Magnification of Eyepiece (ocular)

Total Magnification

Scanning

Low Power

High Power

4X

10X

40X

10X

10X

10X

40X

100X

400X

• How much more powerful is high power compared to the low power in terms of total magnification?

• How much more powerful is high power compared to the scanning in terms of total magnification?

Field of View• The field of view is the white circle you see

through the microscope• As you increase magnification the field of view

decreases

Estimating Size Under a Microscope

• The field of view will have a different diameter depending on which objective you are using

• Scanning is usually a few millimeters in diameter, low and high objective are smaller

• 1mm = 1000 micrometers (μm) or microns