A light microscope (LM) is an instrument that uses visible light and magnifying lenses to examine small objects not visible to the naked eye, or in finer detail than the naked eye allows. Magnification, however, is not the most important issue in microscopy. Mere magnification without added detail is scientifically useless, just as endlessly enlarging a small photograph may not reveal any more detail, but only larger blurs. The usefulness of any microscope is that it produces better resolution than the eye. Resolution is the ability to distinguish two objects as separate entities, rather than seeing them blurred together as a single smudge. The history of microscopy has revolved largely around technological advances that have produced better resolution.
Component of a light microscope and its function:
· Eyepiece - Contain magnifying lens to magnify the image magnified by the objectives lens
· Tube - Connects the eyepiece to the objective lenses
· Coarse Focus - control changes the distance from the subject being examined to the objective lens that's in use.
· Fine Focus - allows for minute adjustments to give very fine control over what is in focus
· Objectives - Magnify the sample in various magnification
· Stage - a platform that supports the specimen
· Stage Clips - to hold the slide in place
· Diaphgram - controls the amount of light which passes to the specimen
· Mirror - serves to direct light into the condenser
THE PART OF LIGHT MICROSCOPE
Most light microscopes have three or four objective lenses on a rotating turret. These lenses magnify the image by 4x to 100x. The light then passes up the body tube to an ocular lens that magnifies the image another 10x to 15x. Research-grade microscopes and the better student microscopes have a pair of ocular lenses so that one can view the specimen with both eyes at once. The lowest power lens is usually 3.5 or 4x, and is used primarily for initially finding specimens. The most frequently used objective lens is the 10x lens, which gives a final magnification of 100x with a 10x ocular lens.
Objective lens:
- 4x objective
- 10x objective
- 40x objective
-100x objective (oil immersion)
OBJECTIVES:
-to provide an experience in the use of microscope
-to illustrate the diversity of cells and microorganism
RESULTS:
 |
| Salmonella Paratypyl (100x magnification) |
 |
| Escherichia Coli, E.coli (40x magnification),pink color |
 | |
| Staphylococcus aureus (40x magnification), purple color |
 | |
| clostridium perfringens (40x magnification), purple color |
 |
| wet mount: culture sample,motile protozoa,pink color |
DISCUSSION
Stained cells:
The light microscope is the apparatus for viewing microorganism. Each group need to learn a simple bright-field microscope correctly by using at least three specimen slide with four objectives wit magnifications 0f 4x, 10x, 40x, 100x.
First, by using Escherichia coli (E.coli), we start at 4x objective, followed by low power 10x objective viewing and the specimen looked clearer at 40x magnification. The shaped of E.coli is rod-shaped and it is a gram-negative bacteria. The gram stain of some specimen either gram-negative or gram-positive can be resulted by looked at their color whether the bacteria are pink or red for gram-negative and blue or purple for gram-positive.
For salmonella paralypyl, magnification at 4x, 10x, and 40x cannot show the clear image of this specimen so, we use the oil immersion (100x). Function of oil immersion in light microscope is used to increase the resolution of a microscope and in order to avoid the loss of clarity associated with refraction. This specimen is aerobic rob and serological identification of somatic and flagella antigens. It is also a gram-negative bacteria because of it color that is pink. The gram-negative bacteria means that they are lack the extra cell wall compare to the gram-positive bacteria.
While for staphylococcus aureus specimen, the image is clearer at 40x magnification. The specimen is purple in color so it is gram- positive coccus. Gram-positive bacteria cell wall typically lack of outer membrane that is found in gram-negative bacteria. The gram-positive bacteria are able to retain the crystal violet because of high amount of peptidoglycan in cell wall.
The wet mount:
The wet mount method was used to determine size and shape of living microorganism. There are some special precautions that being used while applying this method, especially when we want to take one drop of the sample culture. The bottle cover needs to open 45 degree to avoid contamination. When the image is able to see under the microscope, the image is being draw. As stated before, use of oil immersion, make more powerful and high power magnification have short focus length, facilitating the use of oil.
CONCLUSION:
As the conclusion,we able learn to use a simple bright-field microscope correctly.
1.1 Stained cells:
In our experiment we use four objectives with magnifications of 4x, 10x, 40x, 100x.We start at 4x objective, followed by low power 10x objective viewing following by 40x and 100x.The specimen looked clearer at 40x magnification.We can see the shape of the specimen and the colour of the specimen.From microscope’s view we manage to know wether the specimen is gram-negative or gram-positive based on their colour.
Some specimen cannot seen clearly by using magnification at 4x, 10x, and 40x.So we use oil immersion(100x). Function of oil immersion in light microscope is used to increase the resolution of a microscope and in order to avoid the loss of clarity associated with refraction.From this method,we can see specimen clearly.
1.2 The wet mount:
From wet mount methods,we enable to study the sizes and shape of living microorganism.Besides that we enables to determine if the cells are motile.We manage to see the moving specimen by using oil immersion(100x) by using correct method and follow some precautions.
REFERENCE:
2- lab manual
3-http://www.microscope-microscope.org/basic/microscope-parts.htm
No comments:
Post a Comment