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Observing in Biology Index

Observing in Biology Homepage
Making a slide with a coverslip and looking at the slide
using the microscope

Question on the use of the Microscope

Biology Practical Work index

 

Using the compound microscope

Some microscopes may have a mirror instead of a lamp underneath. To get light into the microscope a bench lamp is reflected into the mirror.

The microscope

 

 

WORKING IN THE LABORATORY

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Observing very small specimens

Some specimens that you observe in biology will be so small that you cannot see them with the naked eye. In these cases you will need a much more powerful microscope, called the compound microscope. This microscope can magnify between X40 and X400. To magnify as much we need bigger lenses and more light.

 

Calculating the magnification on a compound microscope

The compound microscope uses two lenses at once: the eye-piece lens and one of the objective lenses. The magnification of the microscope is the product of the magnifying power of these two lenses. This sounds complicated but it is very easy to calculate because the magnification is written on each of the lenses.

 

A compound microscope

 

For example: look on top of the eye-piece lens and you will probably find X10 written on it. The three objective lenses are usually: X4 (low power), X 10 (medium power) and X40 (high power).

If you have a X 10 eye-piece and you are using a X4 objective lens (low power) the total magnification will be: 10x4=X40

If you now turn to a X 10 objective lens (medium power) the total magnification will be: 10x10=X100

 

What would be the total magnification produced by:

  • (1) a X10 eye-piece and a X40 objective?

  • (2) a X15 eye-piece and a X10 objective?

  • (3) a X5 eye-piece and a X4 objective?

 

 

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