2.2 Magnification and calibration

Question 1

What is magnification?

Answer 1

How many times larger the image is than the actual size of the object

Question 2

What do you use to adjust magnification on a compound light microscope?

Answer 2

Interchangeable objective lenses

Question 3

Why is magnification not enough when viewing specimens under a microscope?

Answer 3

Magnification doesn’t increase detail, resolution also needs to be increased.
(resolution manipulates how much detail is seen)

Question 4

What is resolution?

Answer 4

Ability to see individual objects as separate entities

Question 5

What is diffraction?

Answer 5

Tendency of light waves to spread as they pass close to
physical structures
(i.e. the specimen)

Question 6

What limits resolution?

Answer 6

Diffraction of light as it passes through the sample and lenses

Question 7

How does diffraction affect resolution?

Answer 7

Structures in specimens are very close so light reflected from the structures can overlap -> this means the structures are no longer seen as separate entities and detail is lost

Question 8

At what distance can structures in light microscopy no longer be seen as separate entities?

Answer 8

When structures closer than half of the wavelength of light

Question 9

How can resolution be increased?

Answer 9

By using beams of electrons -> shorter wavelength than light waves

Question 10

How do electron beams increase the resolution?

Answer 10

Electrons are still diffracted, but shorter wavelength means individual beams can be closer before they overlap = objects smaller + closer together can be seen separately without blurring from diffraction

Question 11

What is the formula for magnification?

Answer 11

                                           l
                                           l
      Magnification              l               Actual size
                                           l
                                           l