Microscopy

Question 1

What is the maximum resolution of a light microscope?

Answer 1

Around 200nm

(Wavelength of light = 380 - 740nm)

Question 2

What is the maximum resolution of electron microscopes?

Answer 2

0.2 - 0.5nm

(Wavelength of electron = 1nm)

Question 3

How do light microscopes work?

Answer 3

Bright light is focussed onto the specimen using lenses

Light MUST be able to pass through the specimen - dyes often used to distinguish different regions

Appropriate set of lenses needed to focus the image to the eye

Question 4

How do fluorescence microscopes work?

Answer 4

Samples must be stained with fluorescent dye

Incoming light is filtered - only has wavelength that will cause fluorescent molecules to be excited

Only specific wavelength of light is then detected

Question 5

How do confocal microscopes differ to fluorescent microscopes?

Answer 5

Confocal microscopes use lasers to build up a detailed image

Question 6

How must electron microscopes be prepared?

Answer 6

Specimen must be dead and coated with heavy metals - Uranium / lead salts

These must be very thin to allow transmission of electrons

Question 7

What’s the main difference between transmission and scanning electron microscopes? How is this achieved?

Answer 7

Scanning EM produces 3D images - detector measures the QUANTITY of e- scattered or emitted from the sample

Transmission EM produces 2D images

Question 8

What are the main benefits of using light microscopes?

Answer 8

Can be used on living samples

Relatively cheap compared to other methods