Biology
The light microscope Learning objectives: • observe plant and animal cells with a light microscope • understand the limitations of light microscopy.
Key words magnification micrographs resolving power
The type of light microscope you have used in the school laboratory is called a compound microscope. Microscopes magnify the specimen you are looking at, making them look bigger than they are.
Some early microscopes had just a single lens. The compound microscope has two. As lens-making techniques improved, microscopes were developed with higher magnifications and resolutions. Figure 1.4 A compound microscope
Magnification The magnified image is produced by two lenses, an eyepiece and an objective lens. There is usually a choice of objective lenses. Total magnification = magnification of eyepiece × magnification of objective lens For instance, if the eyepiece has a magnification of 10, which is written × 10, and the objective lens has a magnification of × 40, the total magnification is × 400.
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1
Calculate the total magnification with an eyepiece magnification of × 15 and an objective lens magnification of × 40.
2
What magnification would the objective lens need to be to give a total magnification of × 300 with an eyepiece of × 15?
Did you know? British scientist Robert Hooke first used the term ‘cell’. He recorded the first drawings of cells using a compound microscope in his book Micrographia, which was 350 years old in 2015. You may also have heard of Hooke for his law of elasticity, Hooke’s law, in physics.
AQA GCSE Biology for Combined Science: Trilogy: Student Book
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5/20/16 10:04 AM