\nIf you were alive 200 years ago you would have been given some very strange advice on how to avoid getting ill. You might have been told to carry sweet smelling flowers with you or avoid going to smelly places. This was because at that...\nIf you were alive 200 years ago you would have been given some very strange advice on how to avoid getting ill. You might have been told to carry sweet smelling flowers with you or avoid going to smelly places. This was because at that time people didn’t understand that infectious diseases were caused by microorganisms and they didn’t know that because they couldn’t see them. Microorganisms are so called because they can only be seen using a microscope, they are far too small to be seen with ‘the naked eye’. In fact, the invention of the light microscope opened up a whole new world to scientists - the microscopic world. A microscope magnifies objects to make a larger image. This allows us to see objects in more detail. Resolving power, or resolution is also a feature of microscopes. Resolution is the ability to distinguish two different points as being separate. Basically, using a microscope with a high resolution means that you can increase the magnification further without the image becoming blurry. The light microscopes you may use at school will have quite a low magnification and resolution but they will still enable you to view individual cells. To use a microscope you place the slide containing the specimen onto the stage and secure it using the clips. You first choose the lowest objective lens by turning round the nosepiece, this is usually X10 [times ten] magnification. You then turn on the light - this might be by using an electric light or moving a mirror to reflect light onto the specimen. If you look down the eyepiece lens you will see the image but you will probably need to use the focusing knobs to move the stage up and down until the image is clear, and not blurry. You must be careful when moving the stage up not to knock into the objective lens as this might break it. Now you can choose a higher magnification objective lens to see the specimen in more detail. You might have to re-adjust the focus. Now you can clearly see the specimen you can draw it, and write down the total magnification you used. This is calculated by multiplying the magnification of the eyepiece lens (which is normally X10 [times by the magnification of the objective lens. You also need to be able to use the magnification formula: Magnification = size of image / size of real object So, if the diameter of an image of a red blood cell in a book is 1 cm and the actual diameter of a red blood cell is 0.001 cm then the magnification used must be: 1/0.001 = X1000 [one divided by zero point zero zero one equals times one thousand] The microscopic world has been opened up even further due to the invention of the electron microscope. These use beams of electrons to form images and have much higher magnifications and resolutions than light microscopes. They have enabled scientists to study objects in much more clarity and detail, from cell organelles like the nucleus and membrane, to even smaller structures like individual atoms.\n
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