Transmission Electron Microscope

• What does the TEM consist of?

  An electron gun that produces a beam of electrons that is focused onto the specimen by a condenser electromagnet.
• How does a TEM work?

  The beam passes through a thin section of the specimen, parts of the specimen absorb electrons and appear dark, but other parts allow the electrons to pass through and so appear bright.
• Where is an image produced from a TEM?

  On a screen to give a photomicrograph.
• What is the resolving power of a TEM?

  0.1 nm.
• Why can't a TEM resolving power always be achieved?

  Due to difficulties preparing the specimen, and the specimen may be destroyed as a higher energy beam is required.
• What are the limitations of a TEM?

  The whole system must be in a vacuum so living specimens cannot be observed, the image is in black and white, the specimen must be extremely thin, and the image may contain artefacts.
• Why must specimens be extremely thin for a TEM?


  To allow the electrons to penetrate.
• What kind of image does a TEM produce due to the thin specimen?

  A flat, 2-D image.