• Created by: Z Shah
  • Created on: 19-04-15 14:11

How light microscopes work

Light shines through a suitable specimen.  A series of lenses then magnifies the image which is formed.

The specimen, such as a sample of cells, is very thin, so it needs to be supported on a thin glass slide.

The slide and specimen are transparent and allow the visible light to pass through to the magnifying lenses

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How to use a microscope

1.    Always lift the microscope by the body, with the other hand under the base.

2.    Put it on a level surface.

3.    Switch on the microscope.

4.    Turn the focusing knob a very small amount. 

5.    Turn the lowest power objective lens so that it is directly below the tube.

6.    Sit or stand behind the body of the microscope so that you can look down in comfort without tilting it.

7.    Look through the eyepiece so that you can see an even, bright light.

8.    Put the microscope slide onto the stage, fix it on using clips, so that the object you want to look at is directly below the objective.

9.    Adjust the iris diaphragm so field of vision is bright but not dazzling.

10.With your head at the side of the microscope, turn the coarse focusing knob until the objective lens is very close to the slide.  Then, look down the eyepiece lens and use the coarse focusing knob to slowly move the objective lens away from the slide until you can see a very clear, sharp image.  Adjust the fine focusing knob to clarify further.

11.If you need greater magnification, turn to a higher power objective and follow instruction 9 again.

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Making a slide

  1. Carefully wipe a cotton bud along the inside of your cheek.
  2. Gently dab the bud onto a clean microscope slide. 
  3. Place the cotton bud in the pot of alcohol provided.
  4. Add 1 drop of stain to specimen.
  5. Lower the cover slip onto the slide very slowly in order to expel air under the slide.
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Using the microscope to measure

1.    Set up your microscope so that you can see a bright light when you look down the eyepiece.  Remember to always start using the low power objective lens.

2.    Take a piece of graph paper and place it on a clean slide.

3.    Observe the graph paper under low power, focusing carefully so that you can clearly see the small squares.

4.    Use the millimetre squares to measure the diameter of the field of view of your microscope at low power.

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