Apparatus & Techniques: Using an Optical Microscope Flashcards
Method
Preparing a slide using a liquid specimen:
Add a few drops of the sample to the slide using……
Cover the liquid/smear with a coverslip and gently press down to………
Wear gloves to ensure there is no….
pipette
remove air bubbles
cross contmination
How optical microscopes work
Light is directed through the thin layer of biological material that is supported on a glass slide
This light is focused through several lenses so that an image is visible through the eyepiece
The magnifying power of the microscope can be increased by rotating the higher power objective lens into place
Preparing a slide using a solid specimen:
Use scissors to cut a small sample of the tissue
Peel away or cut a ……… layer of cells from the tissue sample to be placed on the slide (using a scalpel or forceps)
Some tissue samples need be treated with chemicals to kill/make the tissue ……..
Gently place a coverslip on top and press down to remove any …………..
A stain may be required to make the structures visible depending on the type of tissue being examined
Take care when using sharp objects and wear gloves to prevent the stain from dying your skin
very thin
rigid
air bubbles
When using an optical microscope always start with the……… objective lenses
what does this allow you to do
low power objective lens:
It is easier to find what you are looking for in the field of view
This helps to prevent damage to the lens or coverslip incase the stage has been raised too high
Preventing the dehydration of tissue:
The thin layers of material placed on slides can dry up rapidly
Adding ……… can stop cell dehydration
water drop
Unclear or blurry images:
Switch to the lower power objective lens and try using the ….. focus to get a better image
Consider whether the specimen sample is thin enough for ………to pass through to see the structures clearly
There could be ……….. with foreign cells or bodies
coarse
light
cross-contamination
Using a graticule to take measurements of cells:
A graticule is a
It can be placed into the …………of a microscope to act as a ruler in the field of view
As a graticule has no fixed units it must be ……….for the objective lens that is in use. This is done by using a ………….
By using the two scales together the number of micrometers each graticule unit is worth can be worked out
After this is known the graticule can be used as a ruler in the field of view
small disc that has an engraved ruler
eyepiece
calibrated
scale engraved on a microscope slide (a stage micrometer)
limitations of optical microscope
The size of cells or structures of tissues may appear inconsistent in different specimen slides
Cell structures are 3D and the different tissue samples will have been cut at different planes resulting in inconsistencies when viewed on a 2D slide
Optical microscopes do not have the same magnification power as other types of microscopes and so there are some structures that can not be seen
Exam Tip
Remember the importance of calibration when using a graticule. If it is not calibrated then the measurements taken will be completely arbitrary!
