RP microscopy

Question 1

magnification equation

Answer 1

image size/actual size

Question 2

eyepiece lens

Answer 2

lens closest to your eye, usually has a magnification of x10

Question 3

objective lens

Answer 3

three lenses of different strengths, can be used to magnify image more clearly

Question 4

stage

Answer 4

place where you put a microscope slide

Question 5

diaphragm

Answer 5

controls amount of light that goes onto microscope slide

Question 6

light/mirror

Answer 6

projects light onto the microscope slide

Question 7

arm

Answer 7

holds eyepiece lens above stage

Question 8

base

Answer 8

stop microscope from falling over

Question 9

fine focus knob (smaller knob)

Answer 9

used to focus image to improve sharpness

Question 10

coarse focus knob (larger knob)

Answer 10

used to focus image so you can see it clear

Question 11

total magnification equation

Answer 11

magnification of eyepiece x magnification of objective

Question 12

(e, l) magnification

Answer 12

electron has a higher magnification (x1000000), light is about (x450 to x600) so electron allows you to see much smaller things in more detail

Question 13

(e,l) price

Answer 13

light microscope much cheaper (£70), compared to electron at £10,000

Question 14

(e,l) colours

Answer 14

light microscope allows you to see in colour, electron is in black and white

Question 15

what do light microscopes use to form an image?

Answer 15

light and lenses

Question 16

what do electron microscopes use to form an image?

Answer 16

electrons

Question 17

(e,l) resolution

Answer 17

electron have a higher resolution

Question 18

resolution

Answer 18

the ability to distinguish between two points

Question 19

method to prepare

Answer 19

1. add a drop of water to middle of a clean slide
2. cut up an onion and separate into layers and use tweezers to peel off some epidermal tissue
3. add a drop of iodine solution to stain and highlight cells
4. place a cover slip on top by slowly lowering down, try to reduce air bubbles
5. place the slide on the stage of the microscope

Question 20

method to observe

Answer 20

1. turn the nosepiece to select a low power objective
2. set up the microscope-use the coarse knob to raise the stage so the end of the objective lens almost touches it
3. turn the coarse adjustment knob to move the lens towards the slide
4. look through eyepiece and turn coarse adjustment knob until the cells come into focus
5. slightly turn the fine adjustment knob to bring the cells into a clear focus
6. turn the nosepiece to switch to a higher power
7. use the fine adjustment knob again to bring the cells back into focus
8. make a clear, labelled drawing of some of the cells, include the magnification

Question 21

safety

Answer 21

1. iodine is an irritant-wear goggles, wash hands

Question 22

equipment list

Answer 22

-microscope
-onion
-iodine solution
-slide
-tweezers
-water
-cover slip
-scalpel

Question 23

why is a thin sample of tissue required?

Answer 23

allows light to pass through so internal structures can be observed

Question 24

why is water added to the slide?

Answer 24

allows the sample to be suspended between the slide and cover slip and ensures cover slip stays in place

Question 25

why is iodine solution added?

Answer 25

it adds contrast, turns blue-black as it reacts with starch allowing structures to become more visible

Question 26

why is the cover slip lowered using a mounting needle?

Answer 26

to ensure that no air bubbles are trapped

Question 27

define magnification?

Answer 27

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

Question 28

how does a light microscope work?

Answer 28

passes a beam of light through a specimen which travels through the eyepiece lens

Question 29

5 advantages of light microscopes

Answer 29

inexpensive
easy to use
portable
in colour
living and dead specimens observed

Question 30

disadvantages of light microscope

Answer 30

limited resolution

Question 31

how does an electron microscope work?

Answer 31

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

Question 32

2 advantages of electron microscopes

Answer 32

greater magnification and resolution

Question 33

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

Answer 33

-allow sub-cellular structures to be observed in detail
-enable scientists to develop more accurate explanations

Question 34

4 disadvantages of electron microscopes

Answer 34

expensive
large so less portable
black and white
training to use
only observe dead specimens