1. The Microscope Practical NO (2) Dalia Kamal Eldien Mohammed

2. Light microscope The optical microscope is the most common type of microscope used in the laboratory, contains several parts with specific functions: 1-Structral components:- o Arm: this part on the side of the microscope is used to supports the microscope when carried. o Base the bottom part of the microscope  Note: When carry the microscope one of your hand in the arm, and the other under the base body

3. 2-Optical components: o Eyepiece: contains the ocular lens, which provides a magnification power of 10x to 15x, usually. This is where you look through. o Nosepiece: holds the objective lenses and can be rotated easily to change magnification. o Objective lenses: usually, there are three or four objective lenses on a microscope, consisting of 4x, 10x, 40x and 100x magnification powers. Note: 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. o Light source: it projects light upwards through the diaphragm, slide and lenses. o Condenser is used to collect and focus the light from the illuminator on to the specimen. It is located under the stage often in conjunction with an iris diaphragm. o Iris Diaphragm controls the amount of light reaching the specimen. It is located above the condenser and below the stage. Note: As a rule of thumb, the more transparent the specimen, less light is required.

5. o Coarse adjustment: this part moves the stage up and down to help you get the specimen into view o Fine adjustment: this part moves the stage slightly to help you sharpen or "fine" tune your view of the specimen o Stage clips: hold the slide in place. o Stage: it is a flat platform that supports the slide being analyzed.

6. Parts of light microscope

8. How Does a Microscope Work? o All of the parts of a microscope work together - The light from the illuminator passes through the aperture, through the slide, and through the objective lens, where the image of the specimen is magnified. o The then magnified image continues up through the body tube of the microscope to the eyepiece, which further magnifies the image the viewer then sees.

9. How to use X 10 lens 1.Turn on the light source& switch to the 10x objective lens. 2.Place the specimen slide on the stage and secure in the proper position. Look at the slide and place it so the specimen is over the light aperture in the stage. 3.Lower the condenser & close the diaphragm 4. Raise the lens using the coarse focus knob until you see the image come into focus and then go out again, then focus back until you find center focus. Adjust fine focus similarly. 5. Center the image and adjust the light using the diaphragm. 6. Recenter and adjust focus, first coarse, then fine focus 7. Readjust diaphragm as needed.

10. How to use X 100 lens  Place a drop of immersion oil on the cover slip over that area, and very carefully swing the oil immersion lens into place.  Focus carefully, preferably by observing the lens itself while bringing it as close to the cover slip as possible, then focusing by moving the lens away from the specimen.  When in focus the lens nearly touches the cover slip. The focal plane is so narrow that it is very easy to focus right past it. If you are focusing toward the specimen, you can drive the lens right into it.

11.  Three important rules attend the use of this lens: 1. Never use an oil immersion lens without the oil. 2.Never get oil on any other lens. 3. Clean up all oil when finished.

12. Practical Using the following labeled slides  Adjust slide A using X 100  Adjust slide B using X 10& X 40 Using the following labeled slides  Adjust slide A using X 100  Adjust slide B using X 10& X 40