lecture 1.2

Question 1

What is the highest practical magnification of a light microscope?

Answer 1

about 1000-1500

Question 2

What is the highest practical magnification of a transmission electron microscope?

Answer 2

over 100,000

Question 3

What is the best resolution of a light microscope?

Answer 3

0.2 um

Question 4

What is the best resolution of a transmission electron microscope?

Answer 4

0.5 um

Question 5

What is the radiation source for a light microscope?

Answer 5

visible light

Question 6

What is the radiation source for a transmission electron microscope?

Answer 6

electron beam

Question 7

What is the medium of travel for a light microscope?

Answer 7

air

Question 8

What is the medium of travel for a transmission electron microscope

Answer 8

high vaccum

Question 9

What is the type of lens for a light microscope?

Answer 9

glass

Question 10

What is the type of lens for a transmission electron microscope?

Answer 10

electronmagnet

Question 11

What is the source of contrast in a light microscope?

Answer 11

different light absorptions

Question 12

What is the source of contrast in a transmission electron microscope?

Answer 12

scattering of electrons

Question 13

What is the focusing mechanism of a light microscope?

Answer 13

adjust the lens position mechanically

Question 14

What is the focusing mechanism of a transmission electron microscope?

Answer 14

adjusts current to magnetic lens

Question 15

What is the method of changing magnification in a ligh microscope?

Answer 15

switch the objective lens or eyepeice

Question 16

What is the method of changing madnification in a transmission electron microscope?

Answer 16

adjust to the current magnetic lens

Question 17

How is the specimen mounted in a light microscope?

Answer 17

on a glass slide

Question 18

How is the specimen mounted in a transmission electron microscope?

Answer 18

on a metal grid, usually copper

Question 19

What are the types of light microscopes?

Answer 19

bright-field microscope
dark-field microscope
phase-contrast microscope
fluorescence microscope

Question 20

How are the images formed?

Answer 20

image formed by action of 2 lenses, are compound microscopes

Question 21

What defines the Phase-Contrast microscope?

Answer 21

excellent way to observe living cells

enhances the contrast between intracellular structures

Question 22

What is a good example of a Phase- Contrast microscope?

Answer 22

Especially useful for detecting bacterial components such as endospores and inclusion bodies that have refractive indices different from that of water

Question 23

How does a Phase-Contrast microscope create an image?

Answer 23

Some light rays from hollow cone of light passing through unstained cell slowed/out of phase (dark against bright background)
Converts differences in refractive index/cell density into detected variations in light intensity

Question 24

How does the Differential Interference Contrast Microscope (DIC) create an image?

Answer 24

creates image by detecting differences in refractive indices and thickness of different parts of specimen

Question 25

What is the Differential Interference Contrast Microscope (DIC) used for?

Answer 25

excellent way to observe living cells. Live, unstained cells appear brightly colored and three-dimensional

Question 26

What is the radiation source for a fluorescence microscope?

Answer 26

ultraviolet, violet, or blue light

Question 27

In a fluroscence microscope, what is the specimen stained with?

Answer 27

Fluorochromes

Question 28

How does a Fluorescence microscope create an image?

Answer 28

shows a bright image of the object resulting from the fluorescent light emitted by the specimen

Question 29

What is a fluorochrome?

Answer 29

fluorochrome-labeled probes, such as antibodies, or fluorochrome dyes tag specific cell constituents for identification of unknown pathogens can be used to localize specific proteins in cells

Question 30

What is red/green dye?

Answer 30

Live cells are stained green where as dead cells are stained red

Question 31

What is the light source for a Confocal Microscope?

Answer 31

laser beam

Question 32

How does a Confocal Microscope create an image?

Answer 32

creates sharp, composite 3D image of specimens by using laser beam, aperture to eliminate stray light, and computer interface

Question 33

How does a Scanning Electron Microscope create an image?

Answer 33

uses electrons reflected from the surface of a specimen to create image produces a 3-dimensional image of specimen’s surface features

Question 34

How does electron cryotomography work?

Answer 34

The speciem goes through rapid freezing and the images are recorded from many different directions to create 3-D structures

Question 35

What does rapid freezing show?

Answer 35

cytoskeletal elements, magnetosomes, inclusion bodies, flagellar motors, viral structures

Question 36

What is the radiation source for 3-D EM tomography?

Answer 36

electron beam

Question 37

How does 3-D EM Tomography create an image?

Answer 37

Images are collected by tilting the specimen in the electron beam and collecting images at 1-2º intervals. Superimposition of image detail is resolved by computing 3-D reconstruction via back-projection algorithms

Question 38

How does a scanning tunneling microscope work/create an image

Answer 38

``` steady current (tunneling current) maintained between microscope probe and specimen Up/down movement of probe as it maintains current is detected, used to create image of surface of specimen ```

Question 39

How much can a scanning tunnelting microscope magnify?

Answer 39

Magnification 100 million times, can view atoms on surface of a solid