MICROSCOPY

Compare and contrast light and electron microscope

Discovered by Romans in the first century AD microscope is one of

if not the most important scientific equipment. Since then

microscopes have been altered as technology grew so they can

give us a clearer picture of the specimen. Today there are two

types of microscopes light and electron microscope. Light

microscope is a type of microscope, which uses light and magnifying

glass to inspect things that are

too small to be seen by the naked

eye, or finer detail than the

necked eye is able to pick up.

Electron microscope is a type

microscope, which fires a highly

energetic electron to study

things that are too small to be

seen by light microscope such as

viruses.

Light microscopes have a

resolution of 200nm, if two object are closer than 200nm they appear as one object

therefore, there is no chance of being able to look at the internal structure of a cell.

This is because light microscopes use light to magnify object if light cannot pass

through the two objects they are not distinguished as separate objects. Electron

microscopes however have a resolution of 0.1nm as electrons are smaller than light

waves and therefore can pick up much more detail than light microscope.

Since electron microscopy uses charged electrons they cannot be fired at anything

and they must be used in a vacuum chamber therefore when preparing the specimen

all moisture must be removed or the water in the specimen will boil and destroying it.

Light microscopes are small and relatively cheap

therefore can be purchased and used for education

purposes electron microscopes however are expensive

and can only be used for medical purposes. Specimen for

light microscope are stained to make it more visible and

to allow contrast between different parts of the cell.

Electron microscope work differently than light microscope, as electrons cannot be

seen the image is projected on to a screen. Unlike light microscopes, the image is

shown in black, white and shades of grey. The colour is then added on special

computer software.

There are two types of electron microscopes

Transmission electron microscope (TEM) and Scanning

electron microscope (SEM). Transmission electron

microscope passes through a thin prepared sample. It

passes through a denser part of the cell less easily giving

some contrast. This type of electron microscope has a

magnification of X5000. However, the electrons damage

thin tissue therefore must be coated with thin layer of

heavy metal such as gold. In Scanning electron

microscope is beamed onto a specimen however, the

electrons do not pass through rather bounce off the sampler creating a 3D image.

However, the magnification is only X1000 so does not pick up as much detail as TEM.

Scanning electron microscope can provide the detail of the external structure rather

like what is formed by the eye whereas Transmission electron microscope probes the

internal structure of solid and gives us the microstructure of cells not seen by the

necked eye. Therefore, we can learn more about what we are made of more

efficiently.

Although both types of microscope are indeed, very helpful nether one is without the

limitation. However they allowed as to explore and see in detail the cell structure of

living organisms developing our ideas of life and its constituency.

BETLEHEM SIRAK FEKADE

BIOLOGY

MR BONNING