Microscope Definitions

Question 1

Refractive index

Answer 1

Measure of how much a substance slows velocity of light

Question 2

Focal point

Answer 2

Point a lens focuses light on

Question 3

Focal length (f)

Answer 3

Distance from the center of the lease to the focal point.

Question 4

Humans can’t see objects closer than?

Answer 4

25cm

Question 5

Lens strength and Focal length

Answer 5

Higher lens strength = shorter focal length

Question 6

Bright field microscope

Answer 6

Bright background with a darker image of the sample

Question 7

Condenser lens

Answer 7

Below stage, focuses light on sample

Question 8

Parfocal

Answer 8

Keeps image in focus when objective lenses are changed

Question 9

Magnification

Answer 9

Product of ocular and objective power

Question 10

Resolution

Answer 10

Ability of a lens to distinguish two objects from each other

Question 11

Numerical aperture

Answer 11

N sin theta n=refractive index theta= half angle of the cone of light entering objective

Question 12

Diameter of smallest resolvable particle

Answer 12

= 0.5 wavelength of light / numerical aperture.
(Smaller this is the better resolution and finer detail observed)

Question 13

What is needed for fine detail characterization?

Answer 13

High quality magnification & resolution (high aperture)

Question 14

Darkfield Microscopy

Answer 14

Produces bright objects against a bright field (only light refracted by specimen enters objective due to hollow cone of light)

Question 15

Phase contrast Microscopy

Answer 15

Relies on change of velocity of light in different media as it passes through the sample.

Question 16

Phase contrast microscope most useful for?

Answer 16

Living samples; creates contrast without staining

Question 17

Condenser annulus

Answer 17

Directs ring of light to the condenser

Question 18

Phase plate

Answer 18

Focuses undeviated light and advances by 1/4 wavelength to create required 1/2 wavelength separation between deviated and undeviated light

Question 19

Fluorescence microscopy

Answer 19

Excites a specimen with a specific wavelength of light, triggers the specimen to emit light

Question 20

Fluorochromes

Answer 20

Fluorescent dyes used to tag specific cells or parts of cells so that they emit light at a specific wavelength.

Question 21

Confocal microscopy

Answer 21

Used laser beam to illuminate a fluorescent sample and remove stray light to produce higher resolution images

Question 22

Fixation

Answer 22

Process used to fix and preserve the internal and external structures of a sample

Question 23

Heat fixation

Answer 23

Application of heat to preserve and rice sample cells to a slide

Question 24

Chemical fixation

Answer 24

Use of chemicals to fix a specimen. Protects fine cellular structure better than heat fixation, often used for electron microscopy

Question 25

Capsule staining

Answer 25

Negative staining that illustrates the presence of a capsule ( stains are acidic so stain background revealing a halo if capsule is present)

Question 26

Flagella staining

Answer 26

Increases thickness of flagella with tannic acid or potassium alum to thicken flagella enough that they are visible with light scope

Question 27

Max resolution limit of light scope

Answer 27

0.2 micrometers

Question 28

Electron microscopy

Answer 28

Uses electrons as the illuminating beam. (Roughly 1000 times better resolution than light scope)

Question 29

Transmission electron microscope

Answer 29

Form image from radiation passed through the specimen. Uses electro magnets to focus instead of glass

Question 30

Scanning electron microscope

Answer 30

Produces an image from electrons reflected from an objects surface