A primitive microscope was invented in 1590 in Middelburg, Netherlands, by the eyeglass makers Hans Lippershey, Zacharias Jansen and his father Hans Jansen. Further, Galileo Galilei improved the instrument by using a set of aligned lenses and called it “occhiolino”, what means “little eye”. In 1625, Giovanni Faber named Galileo Galilei’s “occhiolino” as a compound microscope and this name remains until today.
The optical microscope, the most common type of microscope, contains several parts with specific functions. Observe the picture and find their functions.
1) Eyepiece: contains the ocular lens, which provides a magnification power of 10x to 15x, usually. This is where you look through.
2) Nosepiece: holds the objective lenses and can be rotated easily to change magnification.
3) Objective lenses: usually, there are three or four objective lenses on a microscope, consisting of 4x, 10x, 40x and 100x magnification powers. In order to obtain the total magnification of an image, you need to multiply the eyepiece lens power by the objective lens power. So, if you couple a 10x eyepiece lens with a 40x objective lens, the total magnification is of 10 x 40 = 400 times.
4) Stage clips: hold the slide in place.
5) Stage: it is a flat platform that supports the slide being analyzed.
6) Diaphragm: it controls the intensity and size of the cone light projected on the specimen. As a rule of thumb, the more transparent the specimen, less light is required.
7) Light source: it projects light upwards through the diaphragm, slide and lenses.
8) Base: supports the microscope.
9) Condenser lens: it helps to focus the light onto the sample analyzed. They are particularly helpful when coupled with the highest objective lens.
10) Arm: supports the microscope when carried.
11) Coarse adjustment knob: when the knob is turned, the stage moves up or down, in order to coarse adjust the focus.
12) Fine adjustment knob: used fine adjust the focus.