How to use a microscope and oil immersion
How to use a microscope and oil immersion
This is very helpful.
The most powerful lens of the light microscope is the 100x oil immersion objective. 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. You can see the difference between 400x and 1000x in teh image to the left.
Immersion oil has been formulated so that it has a refractive index identical to that of glass. (It is written on the label of the immersion oil container as n D 25 : record it in your notebook.) Thus there is no refraction of light when it passes from glass to oil and vice versa. You can see the effect of this by removing the glass dropper rod from the oil, and reimmersing it. What happens to the image of the glass rod? How do you explain this observation?
Thus, two changes in refractive index can be eliminated by placing a drop of immersion oil on the specimen, and immersing the 100x oil immersion objective directly into the drop. You should be struck by the clarity that results.
Illustrate the four stage process of using the oil immersion lens:
source of article : http://biology.clc.uc.edu/fankhauser/labs/microscope/Oil_Immersion.htm
This is very helpful.
The most powerful lens of the light microscope is the 100x oil immersion objective. 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. You can see the difference between 400x and 1000x in teh image to the left.
Immersion oil has been formulated so that it has a refractive index identical to that of glass. (It is written on the label of the immersion oil container as n D 25 : record it in your notebook.) Thus there is no refraction of light when it passes from glass to oil and vice versa. You can see the effect of this by removing the glass dropper rod from the oil, and reimmersing it. What happens to the image of the glass rod? How do you explain this observation?
Thus, two changes in refractive index can be eliminated by placing a drop of immersion oil on the specimen, and immersing the 100x oil immersion objective directly into the drop. You should be struck by the clarity that results.
Illustrate the four stage process of using the oil immersion lens:
Three important rules attend the use of this lens:1) Focus very carefully with the 40x objective over the stained specimen on the slide.
(Once focused, do not alter focus for the next three steps!)
2) Rotate turret half way so that the 40x and 100x objectives straddle specimen.
3) Apply a small drop of oil directly on the slide over the specimen.
4) Rotate 100x objective into the immersion oil .
PROTOCOL: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.
source of article : http://biology.clc.uc.edu/fankhauser/labs/microscope/Oil_Immersion.htm