Microscopy

Question 1

When were light microscopes first developed

Answer 1

16th to 17th century

Question 2

How many lenses does a compound light microscope have

Answer 2

`two

Question 3

Objective lens

Answer 3

which is placed near the specimen, producing an magnified image which is magnified again by the eyepiece lens

Question 4

eyepiece lens

Answer 4

the specimen is viewed through this

Question 5

what does the objective/eyepiece lens combination provide

Answer 5

higher magnification and reduced chromatic aberration

Question 6

how is illumination provided

Answer 6

by a light underneath the sample

Question 7

what are the ways to prepare samples

Answer 7

• dry mount
• squash slides
• wet mount
• smear slides

Question 8

Dry mount

Answer 8

solid specimens are viewed as whole or cut into very thin slices (sectioning). the specimen is placed in the centre of the slide and a cover slip is placed over.

Question 9

What would you view through dry mounts

Answer 9

hair
pollen
dust

Question 10

wet mount

Answer 10

specimens are suspended in a liquid such as water or immersion oil, a cover slip is placed on from an angle

Question 11

what would you view through wet mounts

Answer 11

aquatic samples - living organisims

Question 12

Squash slides

Answer 12

a wet mount is prepared first, the lens tissue is used to gently press down on coverslip

Question 13

What do you have to be careful of when preparing squash slides

Answer 13

too much pressure will break the cover slip

Question 14

What would you look at using squash mounts

Answer 14

root tip squashes - cell division

Question 15

smear slides

Answer 15

the edge of the slide is used to smear the sample creating a thin even layer on another slide. A cover slip is then placed over the sample

Question 16

What would you look at through a smear slide

Answer 16

blood
blood cells

Question 17

What is diffraction

Answer 17

bending of light as it passes close to an object

Question 18

What is the crystol

Answer 18

aqueous interior of cells

Question 19

What is the job of stains

Answer 19

increase contrast as different components in cells take up stains to different degrees. they allow components to become visible

Question 20

how to prepare a sample for staining

Answer 20

first sample placed on a slide and allowed to air dry

then heat fixed by passing through a flame

the specimen will adhere to slide and will take up stains

Question 21

crystal violet and methylene blue

Answer 21

positively charged dyes

attracted to negatively charged materials in cytoplasm leading to staining of cell components

Question 22

nigrosin and Congo red

Answer 22

dyes that and negatively charged and are repelled by negatively charged cytosol

these dyes stay outside cells leaving cells unstained and making them stand out

this is a negative stain technique

Question 23

differential staining

Answer 23

can distinguish between two types of organisms that would otherwise be hard to identify.