Cell structures
Organisms are made of cells. Most organisms are multicellular and have cells that are specialised to do a particular job. Microscopes produce magnified images of cells so we can study them in detail.
Cell measurement
Greg Foot explains the main differences between light and electron microscopes
Light microscopes
Most animal cells range in size from 0.01 to 0.05 mm, and plant cells from 0.01 to 0.10 mm.
The human eye can see objects as small as around 0.05 mm. Therefore a microscope is needed to see cells in detail.
Microscopes magnify the image of a specimen - cells, tissues or other structures - so that it appears larger. The type of microscope most used in schools is a compound microscope.
Calculating the magnification of a compound microscope
A compound microscope uses two lenses to magnify the specimen - the eyepiece and an objective lens.
In most microscopes, there is a choice of objective lenses to use. Magnification can therefore be varied according to the size of the specimen to be viewed and the level of detail required.
The magnification of a lens is shown by a multiplication sign followed by the amount the lens magnifies, eg ×10.
Magnification of the microscope = magnification of eyepiece × magnification of objective
So, if the magnification of an eyepiece is ×10 and the objective is ×4, the magnification of the microscope is:
magnification of eyepiece × magnification of objective = 10 × 4 = 40
- Question
If the magnification of an eyepiece is ×10 and the objective is ×40, what is the magnification of the microscope?
10 × 40 = ×400
Calculating the magnification of an image
Microscopes use lenses to magnify the image of a biological specimen so that it appears larger.
The formula to calculate magnification is:
\[\text{magnification} = \frac{\text{size of image}}{\text{real size of object}}\]
The formula shown in a magnification triangle: