Chapter 2: How We See the Invisible World Slides

Question 1

What effect does the wavelength of radiation have on microscopy?

Answer 1

Shorter wavelengths have better resolution and higher magnification.

Question 2

What causes magnification?

Answer 2

The light spreading out from the microscope.

Question 3

What is refraction?

Answer 3

The change of light rays as it passes through one medium to another.

Question 4

What is magnification?

Answer 4

How close the object appears.

Question 5

What is resolution?

Answer 5

How close 2 objects can be and still look apart.

Question 6

What are the two things that affect resolution?

Answer 6

Wavelength and numerical aperture.

Question 7

What is numerical aperture?

Answer 7

How much light actually makes it to your eye.

Question 8

What is contrast?

Answer 8

Differences in intensity between two objects, or an object and its background.

Question 9

What can we do to increase contrast?

Answer 9

Staining.

Question 10

True or False: Contrast is not important in determining resolution.

Answer 10

False.

Question 11

How many lenses does a simple microscope contain?

Answer 11

One.

Question 12

Who used simple microscopes to discover microorganisms?

Answer 12

Leeuwenhoek.

Question 13

How may lenses does a compound microscope contain?

Answer 13

A series of lenses for magnification.

Question 14

How do we determine the total magnification of a compound microscope?

Answer 14

Magnification of objective lens times the magnification of the ocular lens.

Question 15

How does light pass through the microscope?

Answer 15

Light passes through specimen into objective lens.

Question 16

How many ocular lenses are in a compound microscope?

Answer 16

One or two.

Question 17

What do most compound microscopes have to direct light through a specimen?

Answer 17

Condenser lenses.

Question 18

What does oil immersion do?

Answer 18

Reduces light scattering
Increases resolution

Question 19

When is the use of a dark-field microscope best?

Answer 19

When observing pale objects.

Question 20

What light rays enter the objective lens?

Answer 20

Only light rays scattered by the specimen.

Question 21

How does the specimen appear in the microscope?

Answer 21

Specimen appears light against a dark background.

Question 22

Why do we use dark-field microscope?

Answer 22

Increases contrast and enables observation of more details.

Question 23

What do fluorescence microscopes do?

Answer 23

Direct UV light source at specimen.

Question 24

What does UV light increase?

Answer 24

Resolution and contrast.

Question 25

True or False: Some cells are naturally fluorescent; others must be stained.

Answer 25

True.

Question 26

Why do we use fluorescence microscopy in immunofluorescence?

Answer 26

It is used to identify pathogens and to make visible a variety of proteins.

Question 27

True or False: In fluorescence microscopy, the specimen radiates energy back as a shorter, visible wavelength.

Answer 27

False: It radiates energy back as a longer, visible wavelength.

Question 28

What do confocal microscopes do?

Answer 28

Use fluorescent dyes Use UV lasers to illuminate fluorescent chemicals in a single plane

Question 29

What is increased with confocal microscopes?

Answer 29

Resolution is increased because emitted light passes through pinhole aperture.

Question 30

What constructs the 3D images in confocal microscopy?

Answer 30

A computer.

Question 31

What can an electron microscope see?

Answer 31

Detailed views of bacteria, viruses, internal cellular structures, molecules, and large atoms.

Question 32

What can electron microscopes do better than light microscopes?

Answer 32

They have greater resolving power and magnification.

Question 33

What are the two types of electron microscopes?

Answer 33

Transmission electron microscope (TEM) Scanning electron microscope (SEM)

Question 34

Where does electron microscopy take place?

Answer 34

In a vacuum.

Question 35

How does a TEM work?

Answer 35

Electron beam will send electrons through the specimen against the lens, and it picks up the image.

Question 36

How does a SEM work?

Answer 36

Images are formed from electrons bounced off the specimen.

Question 37

Why do we use stains?

Answer 37

Coloring specimen with stain increases contrast and resolution.

Question 38

What is the colored portion of the dye for staining?

Answer 38

Chromophore

Question 39

What are simple stains?

Answer 39

One dye is used to create contrast.

Question 40

What are differential stains?

Answer 40

Dyes different organisms different colors.

Question 41

What are some common differential stains?

Answer 41

Gram stain Acid-fast stain Endospore stain Histological stain

Question 42

What does an HE stain show?

Answer 42

Cell contents (cytoplasm, nucleus, organelles, extracellular, components).

Question 43

What are some simple stains?

Answer 43

Negative stains Flagellar stains Fluorescent stains

Question 44

What do stains for electron microscopy contain?

Answer 44

Chemicals containing heavy metals (gold).

Question 45

When do we use a GMS (gomori methenamine silver) stain?

Answer 45

On tissues.