[Unit 3.2] | The Electron Microscope

Question 1

What makes electron microscopes better than optical ones?

Answer 1

• Shorter wavelength beam so higher resolving power

• 2000x higher magnification

• SEMs produce 3D images

Question 2

What are the disadvantages (3) of electron microscopes?

Answer 2

• Monochrome images

• Vacuum requires dead samples

• Requires very thin samples

Question 3

What are the features of a TEM?

Answer 3

• Higher resolving power than SEMs.

• High energy electron beam penetrates (and may destroy) the specimen
• Sample must therefore also be very thin

• Vacuum: no living samples

• Complex staining process required despite producing a monochrome image

Question 4

What are the features of an SEM?

Answer 4

• Lower resolving power than a TEM

• Sample does NOT need to be thin

• Vacuum: no living samples

• Produces a monochrome image

• Produces a 3D image