microscopy

Question 1

What three factors affect the quality of an Optical Image?

Answer 1

Magnification
Resolution
Contrast

Question 2

Magnification

Answer 2

increase in the relative size of an object

Question 3

Resolution

Answer 3

the smallest objests that can be distinguished as a separate objects

Question 4

Contrast

Answer 4

the degree to which the image of an object stands out from its background

Question 5

diffrence in illumination

light microscope/Electron Microscpe

Answer 5

photones/electrons

Question 6

diffrence in Lenses

light microscope/electron microsope

Answer 6

glass/electromagnets

Question 7

diffrence in medium

light microscope/ electron microscope

Answer 7

air/vaccume

Question 8

diffrence in Specimen

light microscope/electron microscope.

Answer 8

hydrated/ dried

Question 9

diffrence between Visualized

light microscope/ electron microscope.

Answer 9

eye of fil/ Phosphorescent screen or film

Question 10

limit of Resolution

Answer 10

r = 0.61 LAMDA
___________
n sin ALPHA

Question 11

Lamda=

Answer 11

wavelendth of the illuminating radiation

Question 12

N=

Answer 12

diffractive index of the medium between the lens and the object

Question 13

a=

Answer 13

half aperture angle of the lens

Question 14

Numerical Aperture (N.A.)= n sin a

Answer 14

measure of resolving power of a lens fixed for any given lens.

Question 15

Contrast in the Light Microscope:

Types of Contrast

Answer 15

• amplitude contrast (brightfield) colored dyes
• Phase contrast
• interferences contrast
• Differential interference contrast (Nomarski)
• Hoffman modulation contrast
• Darkfield
• Fluorescence

Question 16

Microscopy: Light and Electron

Preperation of tissues for microscopy- several steps required

Answer 16

Fixation
Dehydration
Embededding
Sectioning 
Staining

Question 17

Microscopy: light and Electron

Fixation-

Answer 17

• light microscopy- formaldehyde

* electron microscopy- glutarladehyde and osmium tetroxide

Question 18

Microscopy: light and Electron
Dehydration:

Answer 18

-removal of water; sample has to be embedded in a non-aqueous medium dehydrating agents: alcohol and acetone

Question 19

Microscopy: light and Electron
Embedding:

Answer 19

impregnation with a medium that is sufficently hard to be cut into thin slices

• Paraffin-light microscopy
• plastic-light and electron microscopy

Question 20

Microscopy : Light and Electron

Sectioning:

Answer 20

thin enough sections for the illuminating radiation to pass through it.

Question 21

Microscopy: Light and Electron
Staining:

Answer 21

staining method largely determines what one sees in the microscope.