Microscope

Question 1

resolution

Answer 1

refer to ability of lens to distinguish between 2 points, a specified distance apart.

if not separated/distinguished:

partial (kind of overlap)

or

superimposition of image (completely overlap)

Question 2

resolution depends on:

Answer 2

1) quality/type of lens:
electromagnetic, glass, plastic, polycarbonate

2) magnification: the resolution is inversely proportional to magnification (increase magnification is decrease resolution because the higher the magnification, the smaller the aperture, less light)
3) how specimen has been prepared
4) numerical aperture (the larger the aperture the better the resolution, more light enter)

as magnification increase, aperture decrease, less resolution, less light enter

as magnification decrease, working space increase, aperture increase, resolution increase.

4x,10x,40x,100x

> > > > > > lower resolution , higher magnification, lower aperture

«<

Question 3

wavelength and magnification relation

Answer 3

electron microscope uses electromagnetic lens and ray.

shorter wave length»better resolution

shorter wavelength=higher magnification

wave length to wavelength:

top: crest/hill
bottom: trough/valley

Question 4

limits of microscope in class

Answer 4

white light used in compound microscope resolution limit of structure smaller than 0.2um (less than this cannot be resolved/distinguished)

Question 5

working distance

Answer 5

space between slide specimen and objective lens

higher magnification, shorter working distance (bc lens closer to slide)

Question 6

usefulness of microscope depends on

Answer 6

NOT degree of magnification

but rather, ability to resolve

Question 7

real image vs virtual image

Answer 7

every time you look via ocular lens, you are looking at virtual image of specimen (inverted, upside down)

light ray travel from objective lens (real image) to ocular lens (virtual image)

Question 8

contrast

Answer 8

difference of intensity between object and its background

Question 9

What objective lens is oil used with?

Answer 9

100x objective lens is oil immersion lens

Question 10

Oil benefit

Answer 10

increases numerical aperture, thus improve resolution bc more light ray can enter lens (it reduces refraction)

oil refraction index is similar to glass

Question 11

refraction

Answer 11

bending of light rays and its passing from one medium to another (glass to air, etc)

refraction prevent light from entering the small opening of the high powered objective lens.

Question 12

refractive index

Answer 12

measure of velocity of light as it passes through medium

Question 13

how to increase resolution

Answer 13

decrease magnification

decrease refraction of light (via oil for example)

increase light

increase aperture

Question 14

Cell staining, why is certain areas dark?

Answer 14

methylene blue bc its a basic/CATion dye (positive)

attracted to negative ion. thus the more negative the darker, because stain is attracted and gather there,

thus nucleus is dark stained because DNA/chromosome is highly negatively due to PO4 group.

cytoplasm on other hand is less negative and thus lighter stain.