microscopy

Question 1

Define magnification

Answer 1

The number of times bigger an image
appears compared to the size of the real
object.

Question 2

Define resolution

Answer 2

The smallest distance between two

objects that can be distinguished.

Question 3

How does a light microscope work?

Answer 3

Passes a beam of light through a specimen
which travels through the eyepiece lens,
allowing the specimen to be observed.

Question 4

What are the advantages of light microscopes? (4)

Answer 4

● Inexpensive
● Easy to use
● Portable
● Observe both dead and living specimens

Question 5

What is the disadvantage of light microscopes?

Answer 5

Limited resolution

Question 6

How does an electron microscope work?

Answer 6

It uses a beam of electrons which are focused using magnets. The electrons hit
a fluorescent screen which emits visible light, producing an image.

Question 7

Name the two types of electron microscope

Answer 7

Transmission electron microscope (TEM)

Scanning electron microscope (SEM)

Question 8

What is the advantage of electron microscopes?

Answer 8

Greater magnification and resolution.

Question 9

Why do electron microscopes have a greater magnification and resolution?

Answer 9

They use a beam of electrons which has a shorter wavelength than photons of
light.

Question 10

How have electron microscopes enabled
scientists to develop their understanding
of cells?

Answer 10

● Allow small sub-cellular structures (e.g. mitochondria,
ribosomes) to be observed in detail.
● Enable scientists to develop more accurate
explanations about how cell structure relates to
function.

Question 11

What are the disadvantages of electron microscopes? (4)

Answer 11

● Expensive
● Large so less portable
● Require training to use
● Only dead specimens can be observed

Question 12

How do you use a light microscope to look at a specimen?

Answer 12

1) place slide onto stage
2) use clips to hold slide in place
3) select lowest power objective lens
4) position objective lens so it almost touches the microscope slide by slowly turn the coarse focusing dial
5) look at microscope from side, stop turning dial after objective lens almost touches slide
6) look down eye piece, slowly turn coarse focusing dial, increasing objective lens and slide, til the cells come into focus
7) use fine focusing dial to bring cells into clear focus.

Question 13

how do you figure out the magnification?

Answer 13

size of image
÷
size of real object