Microscopes

Question 1

Define Magnification

Answer 1

How many times larger an image is compared to the actual size of the object

Question 2

Define Resolution

Answer 2

The ability to see two objects that are close together as separate and in detail

Question 3

Light Microscope

Answer 3

Light transmitted through specimen
Magnification - x1500
Resolution - 200nm or 0.2um

Question 4

What organelles are visible under a light microscope?

Answer 4

Nucleus
Nucleoli
Chloroplasts
Cell Wall
Cell Membrane
Cytoplasm

Question 5

Transmission Electron Microscope (TEM)

Answer 5

Electrons transmitted through specimen
2D image
Smaller organelles visible
Shows ultrastructure of organelles
Magnification - x500,000
Resolution - 0.05-2nm

Question 6

Scanning Electron Microscope (SEM)

Answer 6

Electrons bounce off surface of specimen then collected to form 3D surface images of cells and organelles
Magnification - x100,000
Resolution - 5-50nm

Question 7

What makes an electron microscope better than a light microscope?

Answer 7

Electrons have a shorter wavelength so they have a higher resolution and magnification

Question 8

Instead of focusing light with lenses, electron microscopes focus beams of electrons with what?

Answer 8

Electromagnets

Question 9

What are the advantages and disadvantages of light microscopes?

Answer 9

ADV:
-Cheap
-Portable
-See living
-In colour
-Samples easy to prepare
-Don’t take up much space

DISADV:
-Low resolution
-Low magnification

Question 10

Disadvantages of electron microscopes

Answer 10

Complex sample preparation
No colour images
No living feels
Has to be in a vacuum
Expensive

Question 11

Magnification formula

Answer 11

Mag=image÷actual

Question 12

Dry mount

Answer 12

Specimen placed on slide and coverslip added

Question 13

Wet mount

Answer 13

Specimen is placed on a slide and oil is added to it with the same refractive I dec as glass

Question 14

Squash slide

Answer 14

Specimen added to a slide and another slide is used to press down on the specimen to make it thinner

Question 15

What is a stage micrometer

Answer 15

A tiny ruler that is often 1mm/1000um long and has 100 divisions that you can place on the stage of the microscope. This looks bigger at higher magnification

Question 16

What is an eyepiece graticule

Answer 16

A small ruler placed in the eye piece of the microscope this has 100 divisions called EYE PIECE UNITS (EPU) this never changes size even if you change magnification

Question 17

1mm in micrometers and nanometers

Answer 17

1mm=100um
1mm=1,000,000nm

Question 18

Best practise for drawing diagrams

Answer 18

50% of space covered
Clear continous lines
No shading
Labels line ruled don’t cross
Magnification added

Question 19

Best practise for making a slide for light microscopes

Answer 19

Place smaller on slide
Put stains at the edge of the specimen
Lower coverslip at an angle to remove reduce air bubbles
Use blotting to remove excess stain
More stains to improve contrast

Question 20

Why do we stain samples

Answer 20

Improve contrast
Make cell organelles visible
Identify different cell types

Question 21

Names of stains

Answer 21

Crystal violet
Safarin
Methylene blue
Carbol fuchsin
Leishmans stain

Question 22

Electron microscopes sample preparation

Answer 22

Fixation- using chemicals or freezing to solidify sample
Staining- with heavy metal (lead) salts that’s reflect or stop electrons
Dehydration- removing water molecules
Set- in resin to preserve