Microscope

Question 1

What is the equation for magnification?

Answer 1

Size of image/ Actual size of image

Question 2

Explain how to measure thee nucleus of the cells when observing the cells through a light microscope

Answer 2

• use eyepiece graticule
• calibrate graticule, using stage micrometer / detail of calibration / calculate the length of one epu
• measure the diameter of the nucleus in, epu / graticule units
• take repeat measurements and calculate a mean diameter (in epu)
• use calibrated epu to calculate diameter (of nucleus) (in μm) / described

Question 3

How to calibrate stage micrometer?

Answer 3

• Place stage micrometer on stage.
• Line up the scales of the graticule and micrometer.
• Count the number of divisions on the eyepiece graticule equivilent to each division on the micrometer.
• Calcutale the length of one division on the eyepiece graticule.

Question 4

How does a scanning electron microscope (SEM) work?

Answer 4

• it directs an electron beam onto a specimen surface.
• The reflected electrons are amplified to produce an image.

Question 5

How does a light microscope work?

Answer 5

light passes through lenses to produce an enlarged image of a specimen

Question 6

How does a transmission electron microscope (TEM) work?

Answer 6

• It transmits a beam of electrons through the specimen.
• More dense structures absorb more electrons so they are darker.
• Focuses image onto a fluorescent screen.

Question 7

Magnifiction and resolution of a light microscope

Answer 7

x2000 and 200nm

Question 8

Magnifiction and resolution of a TEM

Answer 8

x500 000 and 0.5nm

Question 9

Magnifiction and resolution of a SEM

Answer 9

x500 000 and 3-10nm

Question 10

How is a temporary slide prepared for a light microscope?

Answer 10

• A thin sample of tissue is obtained.
• Stain tissue on slide to make structures visible.
• Add cover slip, avoiding air bubbles.

Question 11

Image appearance of SEM

Answer 11

3D

Question 12

Image appearance of TEM

Answer 12

2D

Question 13

What is the function of a stage micrometer?

Answer 13

To calibrate the eyepiece graticule so it can measure structures

Question 14

Why do samples need to be stained for a light microscope?

Answer 14

Its creates clear contrast between heavily and lightly stained areas to distiguish structures.

Question 15

Magnification

Answer 15

the factor by which the image is larger than the specimen

Question 16

Resolution

Answer 16

the smallest distance by which two objects can be separated and still be distinguished

Question 17

How should the field veiw in microscopy be recorded?

Answer 17

With a sharp pencil, no sketchy lines. With a scale and annotations.

Question 18

How does Laser sccanning confocal microscope work?

Answer 18

• Laser scanning confocal microscopes work by using spot illumination (a laser) across a specimen causing fluorescence from the components labelled with a dye.
• The emitted light is filtered through a pinhole aperture, only light radiated from very close to the focal plane is detected.
• With a sharp pencil, no sketchy lines. With a scale and annotations.

Question 19

State the measurement conversions needed for magnification calculations.

Answer 19

1000 nanometres (nm) = 1 micrometre (um)
1000 micrometres (um) = 1 millimetre (mm)
1000 millimetres (m) = 1 metre (m)

Question 20

What is an artefact?

Answer 20

• An artefact is a visible structural detail caused by processing the specimen and not a feature of the specimen
• e.g. the bubbles that get trapped under the cover slip as you prepare a slide for light microscopy.

Question 21

Magnifiction and resolution of a laser scanning confocal microscope

Answer 21

54x to 17,280x and 200nm

Question 22

Image appearance of laser scanning confocal microscope

Answer 22

2D/ 3D

Question 23

Describe a method the researcher could use to prepare athe epidermis of a crop for inspection under a light microscope

Answer 23

1. Gather a fresh sample of leaves from several of the crops
2. Tear the leaves and use forceps to peel the epidermis cleanly away
3. Place the epidermis onto a clean slide on a drop of water, and place a cover slide upon this, using a mounted needle
4. Wipe away excess water and stain if necessary

Question 24

With a x10 eyepiece lens and x4 objective lens, the stage graticule covers 20 EPU on the eyepiece graticule. Houw much distance does 1 EPU represent?

Answer 24

Stage graticule=1000μm
1000μm covers 20 EPU
1 EPU = 50μm