Biology 3.2 The Electron Microscope

Electron microscope has two main advantages:

• Electron beam has v. short wavelength, can resolve objects well.
• Electrons are negatively charge, beam can be focused using electromagnets.
• Some can resolve objects just 0.1nm apart

However, electrons are absorbed by molecules in the air so near-vacuum must be created.

Transmission Electron Microscope (TEM)

- Consists of electron gun that produces beam of electrons, focused onto specimen by condenser electromagnet.

- Beam passes through thin section of specimen - parts absorb electrons and appear dark, others allow electrons to pass through and appear light.

- Image produced on a screen, can be photographed to give a photomicrograph.

Resolving…