Microscopy

Question 1

What is resolution?

Answer 1

The ability to distinguish to objects from each other

Question 2

What is resolution limit (D)?

Answer 2

The smallest distance between two points on a specimen that can be distinguished as two separate entities.

Question 3

How is resolution increased?

Answer 3

To increase the refractive index
Decreasing the wavelength
Increasing the angular aperture

Question 4

What is the practical limit of resolution of human eye?

Answer 4

0.2mm

Question 5

What is the practical limit of resolution of light microscope and fluorescence microscope?

Answer 5

Light microscope - 200nm
Fluorescence microscope - 100nm

Question 6

What is the greatest magnification light microscope can provide?

Answer 6

1000x
With immersion oil 1400x

Question 7

Give example of immersion oil

Answer 7

Paraffin oil and cedarwood oil

Question 8

Compound light microscope works on what principle?

Answer 8

Amplitude contrast

Question 9

Dark field microscopy uses a central circular disk for what?

Answer 9

To remove the unscathered light

Question 10

What kind of specimen is observed in a dark field microscope?

Answer 10

Transparent, unstained

Question 11

What kind of cells are observed in dark field microscope?

Answer 11

Sperms and flagella

Question 12

Is dark field microscope useful for low resolution?

Answer 12

Yes

Question 13

What kind of image do you get in phase contrast microscope?

Answer 13

Black and white

Question 14

How does phase contrast microscope work?

Answer 14

Deduce the difference in refractive index and thickness of the sample

Question 15

What kind of samples are observed in phase contrast microscope?

Answer 15

Live unstained cell

Question 16

What is the better version of phase contrast microscope and how is it better?

Answer 16

Differential interference contrast microscope is better because it shows live 3D cells

Question 17

What is the light source for fluorescence microscope?

Answer 17

The specimen

Question 18

What is the use of excitation filter in fluorescence microscope?

Answer 18

Helps in providing excitation light to the sample

Question 19

How is fluorescence microscope helpful?

Answer 19

Provides high contrast, specificity, live cell imaging and quantitative analysis

Question 20

Name the dyes used in fluorescence microscope

Answer 20

EtBr
DAPI
Phalloidin peptide
Fluorescein
Rhodamine

Question 21

Why is phalloidin peptide used?

Answer 21

To stain actin filament

Question 22

What kind of light do confocal microscope blocks?

Answer 22

Out of focus light

Question 23

What is the use of confocal microscope?

Answer 23

It provides a 3D image by collecting serial section from thick specimen

Question 24

How does electron microscope has high resolution?

Answer 24

Because the wavelength of electrons are very short and uses electromagnetic lenses.

Question 25

Name the two types of electron microscope?

Answer 25

Scanning electron microscope Transmission electron microscope

Question 26

Which electron microscope forms a 3D image?

Answer 26

Scanning electron microscope

Question 27

Why does scanning electron microscope uses coating of metal?

Answer 27

To increase the solution by increase in the conductivity

Question 28

How is transmission electron microscope helpful?

Answer 28

It forms a 2D image of internal structure of fixed cell.

Question 29

Which kind of microscopy helps in observation of plasma membrane?

Answer 29

Freeze fracturing microscopy

Question 30

Maximum value of angular aperture.

Answer 30

70° Hence sin a is 0.94

Question 31

In freeze fracture electron microscopy, what is used to freeze cells?

Answer 31

Liquid nitrogen

Question 32

What is a cryoprotectant and what is its use?

Answer 32

It helps to prevent distortion from ice crystal formation

Question 33

Give example of cryoprotectant

Answer 33

Glycerol