Transmission electron microscope

Question 1

How does the transmission electron microscope work

Answer 1

TEMs use electromagnets to focus a beam of electrons

This beam of electrons is transmitted through the specimen

Denser parts of the specimen absorb more electrons

This makes these denser parts appear darker on the final image produced (produces contrast between different parts of the object being observed)

Question 2

Advantages of TEM’s

Answer 2

They give high-resolution images (more detail)

This allows the internal structures within cells (or even within organelles) to be seen

Question 3

Disadvantages of TEM’s

Answer 3

They can only be used with very thin specimens or thin sections of the object being observed

They cannot be used to observe live specimens (as there is a vacuum inside a TEM, all the water must be removed from the specimen and so living cells cannot be observed, meaning that specimens must be dead, unlike optical microscopes that can be used to observe live specimens)

The lengthy treatment required to prepare specimens means that artefacts can be introduced (artefacts look like real structures but are actually the results of preserving and staining)

They do not produce a colour image (unlike optical microscopes that produce a colour image)