• Created by: Riya2105
  • Created on: 01-02-20 12:02


Microscopes let us see things that are not visible with the naked eye. The microscopy techniques we can use have developed over the years as technology and knowledge have improved. Light microscopes use light and lenses to form an image of a specimen and magnify it. They let us see individual cells and larger sub-cellular structures like the nuclei, Electron microscopes use electrons instead of light to form an image. They have a much high magnification than light microscopes and also have a much higher resolution. Resolution is the ability to distinguish between two points so a higher resolution gives a sharper image. Electron microscopes let us see smaller things in more detail such as mitochondria and ribosome. 

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Preparing a Slide

A slide is a slip of clear plastic or glass onto which a specimen is mounted. In order to prepare a slide for an onion, you firstly have to add a drop of water to the middle of a clean slide. Then cut up the onion and separate it out into layers. Use tweezers to peel off some epidermal tissue from the bottom of one of the layers. Using the tweezers, place the epidermal tissue into the water on the slide. Add a drop of iodine solution. This is a stain that will highlight objects in a cell by adding colour to them. Place a cover slip on top. 

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Using a Light Microscope

1) Clip the slide you've prepared onto the stage

2) Select the lowest-powered objective lens 

3) Use the coarse adjustment knob to move the stage up to just below the objective lens

4) Look down the eyepiece

5) Adjust the focus with the fine adjustment knob

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