More microscopy

Question 1

What happens in electron microscopy?

Answer 1

Beam of electrons with a wavelength of less than 1nm illuminate the specimen

Question 2

What are the two types of electron microscope?

Answer 2

Transmission electron microscope (TEM): beam of electrons transmitted through the specimen and focused to produce an image
Scanning electron microscope (SEM): beam of electrons sent across the surface of a specimen and reflected electrons are collected. Produces 3d images

Question 3

What is the difference in price between light and electron microscopes?

Answer 3

Light = inexpensive
Electron = expensive

Question 4

What is the difference in portability between light and electron microscopes?

Answer 4

Light = small and portable
Electron = large and needs to be installed

Question 5

What is the difference in sample preparation between light and electron microscopes?

Answer 5

Light = simple, does not lead to distortion
Electron = complex, often distorts material

Question 6

What is the difference in vacuum use between light and electron microscopes?

Answer 6

Light = not required
Electron = required

Question 7

What is the difference in image produced between light and electron microscopes?

Answer 7

Light = natural colour of sample
Electron = black and white images

Question 8

What is the difference in magnification between light and electron microscopes?

Answer 8

Light = up to x2000
Electron = over x500 000

Question 9

What is the difference in resolving power between light and electron microscopes?

Answer 9

Light = 200nm
TEM = 0.5nm
SEM = 3-10nm

Question 10

What is the difference in specimens between light and electron microscopes?

Answer 10

Light = living or dead
Electron = dead

Question 11

What are artefacts?

Answer 11

A visible structural detail caused by processing the specimen and not a feature of the specimen (eg trapped bubbles under cover slip)

Question 12

What is fluorescence?

Answer 12

The absorption and re-radiation of light

Question 13

How does laser scanning confocal microscopy work?

Answer 13

Moves a single spot of focused light across a specimen (point illumination) which causes fluorescence. Emitted light from the specimen is filtered through a pinhole. Can produce both 2d and 3d images

Question 14

What are some features of of the laser scanning confocal microscope?

Answer 14

• Non-invasive
• Produces 2d and 3d images
• Used in diagnosis of eye disease
• Used in development of new drugs