Lesson 4- Electron Microscopy.

Question 1

Define the term “resolution.”

Answer 1

The smallest distance between two points that can be seen as separate entities.

Question 2

How do electron microscopes work?

Answer 2

Electron microscopes use electrons instead of light to produce an image. They were developed in the 1930s to allow scientists to see in greater detail than ever before. The greater resolution is achieved by using high-energy electrons as the light source.

Question 3

How do T.E.M. microscopes work?

Answer 3

Transmission electron microscopes (TEM) produce the most magnified images. They work in a similar way to a light microscope. A beam of electrons passes through a very thin slice of the sample. The beam is focused to produce an image

Question 4

How do S.E.M. microscopes work?

Answer 4

Scanning electron microscopes (SEM) produce a three-dimensional image of a surface. They send a beam of electrons across the surface of a specimen. The reflected electrons are collected to produce an image.

Question 5

Name some advantages and disadvantages of light microscopes.

Answer 5

• Cheap to buy and operate
• Small and portable
• Simple to prepare a sample
• Natural colour of sample is seen unless staining is used
• Specimens can be living or dead
• Resolution up to 0.2 um (2 x 10-7 m)

Question 6

Name some advantages/disadvantages of electron microscopes.

Answer 6

• Expensive to buy and operate
• Large and difficult to move
• Sample preparation is complex
• Black and white images produced; false colour can be added to image
• Specimens are dead
• Resolution up to 0.1 nm (1 x 10-10m).

Question 7

What has the development of electron microscopy led to?

Answer 7

The development of electron microscopy has allowed scientists to see the detail within subcellular structures, such as chloroplasts.