Microscopes

Anton von Leeuwenhoek was the first to use carefully ground magnifying lens to look at living organisms and body fluids. He even examined material that he scraped from between his own teeth.

With his microscopes Leeuwenhoek discovered a whole new world of living things too tiny for the eye to see.

Englishman Robert Hooke was the first to coin the word “cell” when looking at cork under the microscope. The square plant cells reminded him of cells in a monastery.

A Simple Microscope has only one lens – like a magnifying glass.

A Compound Microscope has two lenses – one in the eyepiece and one on the nose. This multiplies the magnification of the image. Can magnify about 1000 times the objects size! Eyepiece Nose

An electron microscope focuses a beam of electrons on the specimen. Can magnify about 1000 times more than the light microscope! Cannot be used to seeing living cells. . . Only a light microscope can look at living things. Dust Mite Gross!!!

Ocular Another name for the eyepiece is Ocular. On most ‘scopes it magnifies 10 times.

The objective lenses are found on the rotating nosepiece. There may be several but only one is used at a time. Most of our ‘scopes have high power and low power objectives. Low Power High Power

On our microscopes, the low power objective magnifies 10 times. On our microscopes, the high power objective magnifies 40 times.

Total magnification= ocular lens x objective lens

Parts of the Microscope

Ocular Arm High Power Objective Low Power Objective Stage Diaphragm Coarse Focus Fine Focus

Field of View Field of view is a way of saying how much of the total image you are seeing through the circular microscope lens. e

e When the magnification increases, the image gets bigger, but the field of view gets smaller – you’re seeing less of the letter “e”.

Measuring with a Microscope     1 2 Use a clear plastic ruler and clip it on the stage and focus it.

The ruler shows a field of view of About 2.25 mm     There are 1000 μ m in one millimeter. 2.25 mm x 1000 = 2250 μ m