The Microscope    Preparing a slide of cheek cells

Using the microscope: Select a low power objective lens Adjust the mirror to produce the best light. Move the objective lens down towards the slide, looking from the side. Focus by moving the lens AWAY from the slide. Adjust the aperture to produce the best light.

The total magnification is found by multiplying the magnification of the eye piece by the magnification of the objective lens
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Preparing a slide of some cheek cells:

• Take a clean microscope slide
• Rub a clean cotton bud around the inside of your mouth and then smear it across the middle of the slide.
• Add one drop of water and a drop of methylene blue stain.
• Place a cover slip on the drop (at an angle so that there are no air bubbles)
• Squash it down gently using a piece of blotting paper
• Place the prepared slide on the microscope stage.
• Adjust the light source so that it shines through the slide.
• Focus by racking the lens AWAY from the slide

The stain helps the different areas of the cells show up.

 
Cheek cells 
Note: A micron (short for micrometer) is one-millionth of a meter.
A human hair is about 50 microns wide

The same procedure can be carried out on the thin skin that can be peeled from an onion. The stain is not needed in this case.

Onion cells