Cell measurement
Greg Foot explains the main differences between light and electron microscopes
Light microscopes
Most animal cells range in size from 10 - 50 渭m, and plant cells from 10 - 100 渭m.
The human eye can see objects as small as 50 渭m. We require a microscope to see cells in further detail.
Microscopes magnify the image of a specimen - a cell, tissue, etc. - so that it appears larger. The type of microscope you use in a school laboratory is as a A microscope in which the lens is close to the sample being magnified..
Calculating the magnification of the microscope
The compound microscope uses two lenses to magnify the specimen 鈥 the The eyepiece, or ocular, is the lens at the top of a compound microscope. It has a longer focal length than the objective lens and magnifies the image produced by the objective. and an In a compound microscope, the lens closest to the specimen has a very short focal length and produces a greatly magnified image of the specimen. .
In most microscopes, there is a choice of objective lenses to use. The amount that an image of something is scaled up when viewed through a microscope. 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 脳10.
So, if the magnification of an eyepiece is 脳10 and the objective is 脳4, the magnification of the microscope is:
magnification of eyepiece 脳 magnification of objective = 10 脳 4 = 40.
Question
If the magnification of an eyepiece is 脳10 and the objective is 脳40, what is the magnification of the microscope?
脳400.
It is 10 脳 40 = 400.
Calculating the magnification of an image
Microscopes use lenses to magnify the image of a biological specimen so that it appears larger. Photographs can be taken through a microscope. Sometimes you may be asked to make measurements from a photograph in order to calculate the actual size of an organelle or its magnification.
The formula to calculate magnification is:
\( \text{magnification} = \frac{size~of~image}{real~size~of~object}\)