What is a microscope for?An instrument for viewing objectsthat are too small to be seeneasily by the naked eye.
HISTORY: Circa 1000AD – The first vision aid wasinvented (inventor unknown) called a readingstone. It was a glass sphere that magnifiedwhen laid on top of reading materials. Circa 1284 - Italian, Salvino DArmate iscredited with inventing the first wearable eyeglasses.
1590Two Dutch eye glass makers, ZacchariasJanssenand son Hans Janssen experimentedwith multiple lenses placed in a tube. TheJanssens observed that viewed objects in frontof the tube appeared greatly enlarged,creating both the forerunner of the compoundmicroscope and thetelescope.
1665 – English physicist, Robert Hooke looked at asliver of cork through a microscope lens andnoticed some "pores" or "cells" in it. 1674 – Anton van Leeuwenhoek built a simplemicroscope with only one lens to examine blood,yeast, insects and many other tiny objects.Leeuwenhoek was the first person to describebacteria, and he invented new methods forgrinding and polishing microscope lenses thatallowed for curvatures providing magnifications ofup to 270 diameters, the best available lenses atthat time.
18th century – Technical innovations improvedmicroscopes, leading to microscopy becomingpopular among scientists. Lenses combining twotypes of glass reduced the "chromatic effect" thedisturbing halos resulting from differences inrefraction of light. 1830 – Joseph Jackson Lister reduces sphericalaberration or the "chromatic effect" by showing thatseveral weak lenses used together at certaindistances gave good magnification without blurringthe image. This was the prototype for the compoundmicroscope.
1872 – Ernst Abbe, then research director of theZeiss Optical Works, wrote a mathematical formulacalled the "Abbe Sine Condition". His formulaprovided calculations that allowed for themaximum resolution in microscopes possible. 1903 – Richard Zsigmondy developed theultramicroscope that could study objectsbelow the wavelength of light. He won theNobel Prize in Chemistry in 1925.
1932 – Frits Zernike invented the phase-contrastmicroscope that allowed for the study of colorless andtransparent biological materials for which he won theNobel Prize in Physics in 1953. 1931 – Ernst Ruska co-invented the electronmicroscope for which he won the Nobel Prize in Physicsin 1986. An electron microscope depends on electronsrather than light to view an object, electrons arespeeded up in a vacuum until their wavelength isextremely short, only one hundred-thousandth that ofwhite light. Electron microscopes make it possible toview objects as small as the diameter of an atom.
1981Gerd Binnig and Heinrich Rohrer inventedthe scanning tunneling microscope that givesthree-dimensional images of objects down to theatomic level. Binnig and Rohrer won the NobelPrize in Physics in 1986. The powerful scanningtunneling microscope is the strongest microscopeto date.
The compound microscope uses lenses and light to enlargethe image and is also called an optical or lightmicroscope. The simplest optical microscope is themagnifying glass and is good to about ten times (10X)magnification.
The compound microscope has two systems oflenses for greater magnification, 1) the ocular, oreyepiece lens that one looks into and 2) theobjective lens, or the lens closest to the object.
Eyepiece Lens: the lens at the top that you look through. They are usually10X or 15X power.Tube: Connects the eyepiece to the objective lensesArm: Supports the tube and connects it to the baseBase: The bottom of the microscope, used for supportIlluminator: A steady light source (110 volts) used in place of a mirror. If yourmicroscope has a mirror, it is used to reflect light from an external lightsource up through the bottom of the stage.
Stage: The flat platform where you place your slides. Stage clips hold the slidesin place. If your microscope has a mechanical stage, you will be able to move theslide around by turning two knobs. One moves it left and right, the other moves itup and down.Objective Lenses: Usually you will find 3 or 4 objective lenses on amicroscope. They almost always consist of 4X, 10X, 40X and 100Xpowers. shortest lens is the lowest power, the longest one is the lens with thegreatest power.Revolving Nosepiece or Turret: This is the part that holds two or moreobjective lenses and can be rotated to easily change power.
Condenser Lens: The purpose of the condenser lens is tofocus the light onto the specimen. Condenser lenses are mostuseful at the highest powers (400X and above).Diaphragm or Iris: Many microscopes have a rotatingdisk under the stage. This diaphragm has different sized holesand is used to vary the intensity and size of the cone of light thatis projected upward into the slide
Proper Handling of the Microscope:The are a number of importantprocedures to follow when using amicroscope. Review the points thatfollow.
1. Always carry the microscope in an upright position with twohands. One hand should support the base and the other shouldbe on the arm.
2. Sunlight should not be usedas a source of light formicroscopes that have amirror rather than aprojection lens.
3. Use lens paper and lens cleaningsolution to clean the lenses on themicroscope. Paper towel will scratch thelenses. Use a soft cloth toClean other partsOf the microscope.
4. Always set your microscope on a clean, flatsurface.5. Always remove slides from the stage androtate the nosepiece to the lowest powerbefore returning the microscope to itsstorage area.