1.2.2(d) use of a light microscope at high power and low power, including use of a graticule Flashcards
how large a sample yields the best results?
a small sample yields the best results
staining a wet mount
For a wet mount only use one or two drops of stain at one end of the sample
how to avoid any air bubbles.
Carefully and slowly lower the cover slip down onto the sample at an angle using a mounting needle to help lower it
how to remove any excess stains and ensure the stain is even
To remove any excess stain and to pull the stain evenly over the sample place a small piece of absorbent paper e.g. blotting paper or paper towel at the edge of the other end of the cover slip to where the stain was first applied, this will pull the liquid across the sample and absorb the excess.
what do you use to help position the sample
foreceps
To use a microscope:
Clean lenses with lens tissue.
ensuring that the slide is clean Place slide to be observed under both clips on the stage, .
Turn the lowest power objective lens on the nosepiece so it is clicked into position.
Looking from the side of the microscope gently turn the coarse adjustment knobs until the lens is just above the slide. It must not touch the slide.
Look down the microscope and adjust the mirror or condenser to obtain the best even illumination
Look down the microscope again and slowly turn the coarse adjustment knobs so the low objective lens and the slide move gradually further apart.
Continue slowly until the object on the slide is in focus.
Then turn the fine adjustment knobs to obtain the best image, the slide might have to be slightly moved to centre the part to be observed.
Once the low power focus has been determined there should be very little adjustment to achieve high power magnification.
Move the slide to the area to be viewed under high power.
Gently rotate the nose piece until the high power objective lens clicks into position.
The fine adjustment knob may have to be turned to improve the focus of the object being viewed.
The light may also have to be slightly adjusted by moving the mirror and/or diaphragm.
should you try and find an object under high power when it cant be found under low power?
NO!
why keep both eyes open when using a microscope?
it helps to prevent eye strain.
how to calibrate an eyepiece graticle
viewing this stage micrometer with an eyepiece graticule in place and using the desired objective lens
line up the graticule markings with those on the stage micrometer.
calculate the calibration factor, indicating how far apart the graticule markings are when using this particular objective lens.
The stage micrometer can then be removed and the specimen slide put in its place.
Measurements of the specimen can be taken using the calibrated graticule.
