3.8 - Electron Microscopes

Question 1

Resolution and magnification of SEMS

Answer 1

• Resolution- Maximum of around 5 nm.
• Magnification- Maximum of around x 1,500,000.

Question 2

SEMs (how do they form an image and what type of images do they form, in what state do the specimens have to be)

Answer 2

• scan a beam of electrons across the surface of a specimen. Reflected electrons are then used to form an image.
• produce 3D images
• can only view non-living ordead specimens. However, SEMs can be used on thicker specimens.

Question 3

Resolution and magnification of a TEM

Answer 3

• Resolution- Maximum of around 0.5 nm
• Magnification- Maximum of around x 1,500,000

Question 4

TEM (what do they do and how does an image form - what type of image is formed and how must the specimen be to be viewed):

Answer 4

• use electromagnets to transmit a beam of electrons through a specimen. The denser parts absorb more electrons, so appear darker in the image formed
• produce high-resolution images, meaning they can be used to observe the internal structures of organelles
• the specimen must be viewed in a vacuum, meaning only non-living or dead organisms can be observed. Also, the specimen must be thin to allow electrons to pass through

Question 5

What images do EMs form and what types of preparation do they require?

Answer 5

• only produce images in black and white
• require complex preparation of specimens, meaning they are more likely to create artefacts. Artefacts are visible details that aren’t part of the specimen being observed, such as air bubbles or fingerprints

Question 6

two types of EM

Answer 6

1. Transmission electron microscope (TEM)
2. Scanning electron microscope (SEM)

Question 7

Why do electron microscopes have a higher resolution than light microscopes?

Answer 7

Electron microscopes use electrons rather than light to form an image. Since electrons have a shorter wavelength than light, electron microscopes have a better resolution than light microscopes.