Microscope 1. Objective Learn The Basic Techniques For The Bacterial

Microscope 1. Objective Learn the basic techniques for the bacterial experiment. Know how to use Immersion oil microscopy. 2. Introduction Since its invention, the microscope has been a valuable tool in the development of scientific theory. Magnifying lenses have been known for as long as recorded history, but it was not until the advent of the modern compound light microscope that the device was used in biology. A compound microscope is composed of two elements; a primary magnifying lens and a secondary lens system, similar to a telescope. Light is caused to pass through an object and is then focused by the primary and secondary lens. The function of any microscope is to enhance resolution. The microscope is used to create an enlarged view of an object such that we can observe details not otherwise possible with the human eye. Because of the enlargement, resolution is often confused with magnification, which refers to the size of an image. In general, the greater the magnification, the greater the resolution, but this is not always true. There are several practical limitations of lens design which can result in increased magnification without increased resolution. 3. Procedure 1) The usage of microscopy Use both hands when lifting or moving the microscope(s). Remove the plastic cover, fold it, and return it to the microscope locker. Unwrap the cord keeping the rubber band on the cord if one is present. Get a rubber band from the instructor if one is not present and place it on the cord. Check to see if the microscope light switch is turned off and the light dimmer knob is at the lowest setting. Turn the light switch off if it is on and place the dimmer switch to the low setting if it is set higher. Plug the microscope into the socket in front of you. Again make certain that the light dimmer is at the low setting. Then turn on the light switch. Put the low power objective in place if someone did not put the scope away correctly. Always move the lower power objective to the use position when finished and putting the scope away. Gently lower the stage by using the course adjustment knob. Get a slide and place it in the slide "positioner" on the stage. (If you use Immersion oil, drop about 3 drops of oil into the slide and carefully turn down the extension tube till the objective lens touch the oil) Move the material over the stage condenser lens by moving the "positioner" knobs.

Use the course adjustment knob to raise the stage until it stops. Adjust the distance between the binocular lenses to fit your eyes. Look into the binocular lenses. If you can see nothing, check to see if the light is on and the light intensity is bright enough....adjust by the light dimmer knob. You may have to turn the fine focus knob four or five turns in each direction. If nothing comes into focus, call the instructor and he/she will adjust the scope. Bring the material into clear focus by using the fine focusing knob. Move the slide by using the slide positioning knobs until you have viewed all of the material on the slide. Position what you wish to see at a higher magnification in the center of the stage condenser lens...that is in the center of what you are seeing. Check again to make certain that the material is in focus. If not, bring it into focus by using the fine focusing knob. Increase the magnification by grasping the nose piece and rotating the next power object in place. While doing this, carefully look at the slide on the stage and the objective. Bring the material into focus by using the fine focusing knob. Only use the fine focusing knob when focusing with the 10X (medium) power and 40X (high power) objectives. The course focusing knob is to only be used with the 4X (low power) objective. Repeat this above procedure when increasing magnification from the 10X to the 40X objectives. Light intensity can be adjusted by either turning the light dimmer knob or moving the lever on the iris diaphragm. When finished using the scope you must return it using the reverse procedures as when you began by doing the following. Make certain no slide is left on the scope. Clean all moisture and materials from the scope. Make certain the slide "positioner" is positioned on the stage surface and not extending over either side of the stage. Put the low power objective in place. Turn the light dimmer to the low setting. Turn off the light switch. Unplug the light cord, wrap and secure it with the rubber band.....as you found it when you began. Replace the cover correctly. Notice that the cover is form fitted. Carefully replace the scope into the locker as you found it. 2) Microscopic measurement We use special slides with scale to measure the bacteria. The ocular was rotated until it superimposed the lines of the ocular micrometer upon those of the stage micrometer. The lines of the ocular micrometer superimposed upon those of the stage micrometer are the points of coincidences.

Each space of the stage micro meter equals 10μm in distance and amount of ocular divisions are equivalent to one stage division was calculated as the number of microns in each space of the ocular scale. The stage micrometer then was replaced with the stained cell slide, the dimensions of each type of cell is measured with the ocular micrometer.

4. Result Use the Immersion oil microscopy, can observe the bacteria in details. 5. Discussion. Why use Immersion oil to observe the bacteria? Because light is refracted every time it passes through a medium with a different refractive index, (air to glass or vice versa) the quality of the image is reduced with each passage. Thus, by reducing the number of such passages to a minimum, the clarity, brilliance and resolving power is preserved. Immersion oil has been formulated so that it has a refractive index identical to that of glass. Thus there is no refraction of light when it passes from glass to oil and vice versa. 6. Conclusion Microscope is a very important tool for biology, without it, lots of experiments cannot be done. If you want to see certain organisms more clear, use Immersion oil microscopy. 7. Reference

The notes that teacher gives. http://homepage.smc.edu/hodson_kent/Cells/microsc_useB3.htm http://biology.clc.uc.edu/fankhauser/labs/microscope/Oil_Immersion.htm