Immersion Oil

Immersion Oil

Postby Stuart Bates » Fri Sep 28, 2012 12:13 pm

Hi all

I just wanted to check whether I am using immersion oil correctly.

When using my x100 objective I place a small drop of oil onto the coverslip directly over the specimen. I then bring round the x100 objective, making sure that it comes into contact with the drop of oil. I then bring the image into focus as normal.

I just assumed this was the normal way of doing it but then I saw some references online that suggest you also need to place some oil on the underside, between the slide and the condenser. :?

Is this correct and if so do you all use this method?

Thanks
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Re: Immersion Oil

Postby Chris Johnson » Fri Sep 28, 2012 5:20 pm

Hi Stuart,

What you are doing is correct. I have never heard of anyone putting oil on the underside of the slide, which isn't necessary.

Chris
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Re: Immersion Oil

Postby Stuart Bates » Fri Sep 28, 2012 8:26 pm

Hi Chris

Thanks for answering my question... it didn't make sense to me either as to why you would put oil under the slide, but I have seen it mentioned on the following website:

http://www.cargille.com/immersionoilmicroscope.shtml

Some quotes are:

"Whereas an objective must be used "dry" or "oiled," depending on design, a condenser will work oiled or dry, but will be limited to a working value. Full resolution of a condenser, N.A. 1.25, can be obtained by "oiling" with water (1.33), or immersion oil (1.515)"

"The condenser working N.A. is only equal to the designed N.A. when it is oiled to the slide..."

"The condenser should be oiled in a low position and, after positioning the slide, raised slowly to make contact."

With my basic knowledge I figured it is something to do with achieving maximum resolution by removing the "air" gaps between the light source and the objective... or something like that!! :lol:
Stuart Bates
 
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Re: Immersion Oil

Postby Leif Goodwin » Fri Sep 28, 2012 8:43 pm

Stuart Bates wrote:Hi Chris

Thanks for answering my question... it didn't make sense to me either as to why you would put oil under the slide, but I have seen it mentioned on the following website:

http://www.cargille.com/immersionoilmicroscope.shtml


I read up on this some time ago, and came to the conclusion that for optimal resolution at high powers e.g. x100 objective, you had to place oil between the condenser and the slide. I tried it, and it is a right royal pain to do, as the slide sticks to the condenser, and becomes hard if not impossible to move. So don't bother. And as Chris indicates, the method is not widely used. I think most mycologists only place oil between the slide and the objective.
Fungi and Nature Photography: http://www.leifgoodwin.co.uk/Fungi/Fungi.html
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