Robert Hooke Theory

Introduction The English Scientist, Robert Hooke (1635-1703), was the first to publish work based upon the use of an optical microscope, in 1665. He was the first to use the word “cell” in the biological context. Hooke used a compound microscope, having two lenses, whereas Antoni Van Leeuwenhoek, a Dutch cloth merchant and Amateur Scientist, used only a single glass lens in his simple microscope, some 10 years or so later. Leeuwenhoek made observations on bacteria, plants, blood cells and minerals and is generally considered to have made a greater contribution to our understanding of the microscopical world than Hooke. Around 1870, Ernst Abbe formulated his famous sine theory for the resolving power of the light

It is the simplest type of microscope. Based on the simplicity of the microscope, it is categorized into two. They are: -

1) Simple microscope

2) Compound microscope

Simple microscope It uses only a single lens, for example: - hand lens. Most of these are double convex or Plano convex lens. Fig.1.2 https://upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Revolving_light_microscope.jpg/220px-Revolving_light_microscope.jpg

Compound microscope Compound microscope uses two lenses. One of the lenses is to form an enlarged image of the object and the second is to magnify the image formed by the second. The modern compound microscope consists of two lens system, the objective lens and the occular lens (eye piece). The first magnified image obtained with objective lens, is again magnified by the eye piece to give a virtual inverted image. The total magnification is the product of the magnifications of the two lens system. Fig. 1.3 https://www.tedpella.com/mscope_html/22460-10.jpg

Parts of a microscope It consists mainly of three parts: -

i. Mechanical part- base, c-shaped arm and stage. ii. Magnifying part- objective lens and ocular lens. iii. Illuminating part- sub stage condenser, iris diaphragm, light

These are used to remove oil from the lens of a microscope.

6) If the microscope is not used for a long period of time, place it in a large, sealable plastic bag. Place a few packets of silica gel into the bag before sealing it. This will keep the air inside the bag dry and prevent mold from forming.

7) Keep the metal parts of the microscope lubricated with silicone grease. This should be at least done twice a year.

Precautions for handling optical equipment

• Never strain, twist, or drop objectives or other optical components. Optics for polarization microscopy are especially susceptible to failure due to mishandling.

• Never force the focus controls of the objective or condenser, and always watch lens surfaces as they approach the specimen. This is especially important for high-power oil immersion lenses.

• Never touch optical surfaces. Just touching an optical surface can remove unprotected coatings and ruin filters which cost a lot of money.

Care and cleaning of optics

Scratches and abrasions Never wipe the surfaces of objectives with paper or cloths. All objectives contain an exposed optical surface that must be protected from abrasion. The stick end of a cotton swab applicator is strong enough to place a permanent scratch mark on the front lens element with a single