2.1 microscopes

Question 1

magnification of optical microscope

Answer 1

x1500

Question 2

resolution of optical microscope

Answer 2

200nm

Question 3

advantages of optical microscope

Answer 3

-simple and cheap
-observes living animals
-produces colour images

Question 4

what image does an optical microscope produce

Answer 4

colour

Question 5

limitations of optical microscope

Answer 5

-limited resolution
-cannot see small organelles

Question 6

why does optical microscopes have limited resolution

Answer 6

due to the short wavelength of visible light

Question 7

how do scanning electron microscopes work

Answer 7

-beam of electrons scan the surface
-detects reflected electrons

Question 8

what does scanning electron microscopes show

Answer 8

-surface structure
-3D images

Question 9

resolution of electron scanning microscope

Answer 9

1-10nm

Question 10

limitations of electron scanning microscope

Answer 10

-vacuum is required
-cannot study living samples

Question 11

how does transmission electron microscopes work

Answer 11

electrons pass through very thin samples

Question 12

what does transmission electron microscopes show

Answer 12

-internal structure
-2D

Question 13

what is magnification

Answer 13

How much bigger an image appears compared to the original object calculated

Question 14

what is resolution

Answer 14

The ability to distinguish two different points in a specimen.

Question 15

why do electrons give a better resolution

Answer 15

-electrons have much shorter wavelengths than visible light
-therefore can distinguish objects closer together

Question 16

describe the steps to preparing a microscope slide

Answer 16

1. obtain a thin specimen
2. use forceps and place in the centre of the slide
3. add a drop of a stain
4. lower the coverslip at an angle
5. use tissue to remove excess liquid

Question 17

why should you use a thin specimen for optical microscopy

Answer 17

as light microscopes rely on light passing through the specimen

Question 18

why is a stain used

Answer 18

-as most cells are colourless or transparent
-stains make structures visible and increase contrast

Question 19

why is the coverslip lowered at an angle

Answer 19

-prevents air bubbles

Question 20

what is an iodine stain used for and what organelles does it stain

Answer 20

-plant cells
-stains: starch and nucleus

Question 21

what does methylene blue stain and what organelles does it stain

Answer 21

-animal cells
-stains: nucleus

Question 22

what does eosin stain and what organelles does it stain

Answer 22

-animal tissues
-stains: cytoplasm

Question 23

what does toluidine blue stain and what organelles does it stain

Answer 23

-plant tissues
-stains: cell walls

Question 24

strict rules on drawing biological molecules

Answer 24

-draw clear single lines
-no shading
-straight arrow labels
-include a scale that represent actual size

Question 25

what is 1 mm in ym

Answer 25

1000ym

Question 26

1ym in nm

Answer 26

1000nm

Question 27

how does a laser microscope work

Answer 27

Laser beam to illuminate the living specimen, scanning it point by point. Fluorescent stain is used on cells

Question 28

what can laser microscopes view

Answer 28

whole cells and tissue

Question 29

what type of image does a laser microscope produce

Answer 29

colour and 3D

Question 30

what must be done before using an eyepiece graticule

Answer 30

calibrate it