B1.1.3 Light Microscopy

Question 1

How light microscope works

Answer 1

passes light through an object
cells placed on slide on stage
then light passes through two glass lenses
lenses magnify object 
then see in more detail

Question 2

How to observe through light microscope?

Answer 2

1. move stage to lowest point
2. select object lens with lowest magnification
3. place slide with cells on it on the stage
4. turn coarse focus knob slowly until you see your object
5. turn fine focus knob until object comes into clear focus
6. to see cells in greater detail - repeat steps with higher magnification objective lens

Question 3

Why stain cells?

Answer 3

• many cells are colourless

- often stain them to make them easier to observe

Question 4

common stains

Answer 4

methylene blue - easier to see nucleus of animal cell
iodine - easier to see plant cell nuclei
crystal violet - stains bacterial cell wall

Question 5

resolution of microscope

Answer 5

smallest distance between two points that can be seen as two entities

Question 6

electron microscope

Answer 6

uses electrons instead of light to produce an image

Question 7

Transmission electron microscope (TEM)

Answer 7

beam of electrons passes through a very thin slice of sample

beam focused to produce an image

Question 8

Scanning electron microscope (SEM)

Answer 8

send beam of electrons across surface of a specimen

reflected electrons = collected to produce an image