magnification

Question 1

magnification definition

Answer 1

• How many times bigger an image appears, compared to the real specimen.

Question 2

Resolution definition

Answer 2

The ability of a microscope to distinguish between 2 points that are close together.

Question 3

cm to mm

Answer 3

x10

Question 4

mm to micrometer

Answer 4

x1000

Question 5

micrometers to nanometres

Answer 5

x1000

Question 6

nanometres to micrometers

Answer 6

/1000

Question 7

micrometers to mm

Answer 7

/1000

Question 8

mm to cm

Answer 8

/10

Question 9

uses of a light microscope

Answer 9

uses light rays to observe object

Question 10

advantages of light microscope

Answer 10

• Can observe living things
  -Does not use harsh chemicals
• Easy to set up and use
• Cheap and portable

Question 11

Disadvantage of light microscope

Answer 11

• Low magnification (up to 2000 times)
• Low resolution

Question 12

Uses of transmission electron microscope

Answer 12

• Uses focussed beams of electrons through sections of tissues.

Question 13

Uses of scanning electron microscope

Answer 13

Uses focussed beams of electrons reflected off the tissues.

Question 14

Advantages of transmission and scanning electron microscope

Answer 14

• High magnification
• High resolution
• Can see details inside cells - T.E.M
• Can see details of the surfaces of the structures S.E.M

Question 15

Disadvantages of TEM and SEM

Answer 15

-Can only see dead materials
- Harsh chemicals used in preparation which can cause artefacts
- Expensive

Question 16

Uses of scanning confocal microscope

Answer 16

Uses a laser beam of light to illuminate chemical stains within the specimen. These then fluoresce.

Question 17

Advantages of laser scanning confocal microscope

Answer 17

• Can see living cells
• Can observe cell processes by tracking molecules
• Higher resolution than light microscope

Question 18

Disadvantages

Answer 18

• More expensive than light microscope and more complex

Question 19

How do we use optical microscope?

Answer 19

• Clip the slide you prepared onto stage.
• Select lowest-powered objective lens.
• Use course adjustment knob to move objective lens down to just above slide.
• If you need to see slide with greater magnification, swap to high-powered objective lens and refocus.

Question 20

How to prepare microscope slide?

Answer 20

• Start by pipetting a small drop of water onto centre of slide.
• Use tweezers to place thin section of specimen on top of water drop.
• Add stain to sample.
• Finally, add cover slip. Stand slip upright on slide, next to water droplet. Then carefully tilt and lower, so covers specimen. Try not to get air bubbles, as it will obstruct view of specimen.

Question 21

Why do we stain specimen?

Answer 21

• Adds contrast to image, some parts of sample will take up stain, other parts won’t.
  -Makes image visible.

Question 22

Why do we use a thin section of specimen on slide?

Answer 22

-To let light through it, so it can be seen more clearly.

Question 23

Explain gram stain technique.

Answer 23

-Apply crystal violet.
-Apply iodine to fix dye.
- Gram positive bacteria will appear blue, purple.
- Gram negative doesn’t take up crystal violet, so add safranin, which is a counter stain, will then turn red.