MICROSCOPY

Question 1

What are the disadvantages of the scanning electron microscope? (3)

Answer 1

-samples have to be placed in a vacuum.

-very expensive.

-sample preparation complicated and expensive.

Question 2

What are the advantages of the scanning electron microscope? (2)

Answer 2

-similar to electron microscope (magnification is only x100,000)

-produces 3D images that can show details of tissue arrangements.

Question 3

How does a scanning electron microscope work? (2)

Answer 3

-3D samples are scanned, these samples are placed in a vacuum in specimen chamber.

-the microscope sends a beam of electrons that interacts with the surface of the specimens showing surface detail.

Question 4

What are the limitations of the electron microscope? (3)

Answer 4

-samples have to be placed in a vacuum.

-very expensive.

-sample preparation complicated and expensive.

Question 5

What are the advantages of the electron microscope? (2)

Answer 5

-high magnification.

-high resolution 0.2nm therefore see more detailed images and smaller specimens.

Question 6

What is the magnification of an electron microscope? (1)

Answer 6

X500,000

Question 7

What is an electron microscope? (3)

Answer 7

-electron beam passes through a very thin prepared sample.

-electrons pass through denser parts of sample less easily creating contrast.

-produces 2D images.

Question 8

What is a light microscope? (1)

Answer 8

Uses light to view an object, also known as a compound microscope because each lens contains more than one glass lens.

Question 9

What is thee function of the condenser lens? (1)

Answer 9

Focuses light before it hits the specimen to be viewed (near the base).

Question 10

What is the function of the eyepiece lens? (1)

Answer 10

The one you look down.

Question 11

What is the function of the coarse focus? (1)

Answer 11

The stage or the objective lens moves a greater distance than if you turn the fine-focus screw.

Question 12

What is the function of the stage? (1)

Answer 12

Where you place the specimen to be viewed.

Question 13

What is temporary preparation? (1)

Answer 13

Involves placing tissue on a glass slide, covering it with a water-based liquid to prevent it drying out and putting an extremely thin glass cover slip over it.

Question 14

What is permanent preparation? (1)

Answer 14

The water has been removed from the tissue and been replaced by a finer substance, the cover slip is held in place by resin.

Question 15

What is a stain? (1)

Answer 15

Used to help you see their structures.

Question 16

What is the resolution of a light microscope? (1)

Answer 16

2 micrometers. (200nm)

Question 17

What is the resolution oof an electron microscope? (1)

Answer 17

5nm.

Question 18

What are the limitations of the light microscope? (2)

Answer 18

-most only magnify to a max of x1500

-maximum resolving power is 200nm, therefore detail is limited.

Question 19

What are the advantages of a light microscope? (4)

Answer 19

-view a direct image.

-inexpensive and portable allowing wide use in education, lavatory analysis and research.

-food for viewing relatively large specimens.

-easy to prepare samples.

Question 20

How does a light microscope work? (2)

Answer 20

-Light passes through the bulb under the stage and through the specimen more light passes through the less dense regions of the cell, creating contrast.

-the image is magnified by objective and eyepiece lenses.

Question 21

Convert cm to mm and vice versa (2)

Answer 21

Cm to mm =x10
Mm to cm = /10

Question 22

Convert mm to micrometer and vice versa (2)

Answer 22

Mm to micrometer= x1000
Micrometer to mm= /1000

Question 23

Convert micrometer to nm and vice versa (2)

Answer 23

Micrometer to nm= x1000
Nm to micrometer= /1000

Question 24

What is the formation for standard form? (1)

Answer 24

Nx10(n)

Question 25

What is magnification? (1)

Answer 25

The degree to which the size of an image is larger than the image itself.

Question 26

What is resolution? (1)

Answer 26

The degree to which its possible to distinguish between two objects that are very close together.

Question 27

How do you calculate magnification? (1)

Answer 27

Magnification= image size/actual size

Question 28

What stains ram positive bacteria, in terms of bacteriology? (1)

Answer 28

The cell wall becomes purple when stained by crystal purple.

Question 29

What stands gram negative bacteria, in terms of bacteriology? (1)

Answer 29

The high lipid content of its outer membrane prevents the crystal violet stain getting to the cell wall, so the bacteria does not become purple, thus not staining.

Question 30

How can you see the chromosomes of a cell, in terms of microscopy? (2)

Answer 30

-with a light microscope you can only see chromosomes when the nucleus divides.

-other times they appear dispersed as a diffuse network.

Question 31

How can you see organelles like chromatin, chromosomes and the nucleolus, in terms of microscopy? (1)

Answer 31

Are only usable if stained with a certain dye.

Question 32

What is a eye graticule? (1)

Answer 32

A small piece of glass with a measurement scale on its surface and fits inside a microscope eyepiece.

Question 33

What is calibration? (1)

Answer 33

A comparison of the scale on the eyepiece reticle with the scale markings of a known dimension on a scale micrometer.