Magnification and calibration - 2.2 (3)

Question 1

To measure the size of a sample under a microscope, what do you use?

Answer 1

an eyepiece graticule

Question 2

What can the true magnification of the different lenses of a microscope vary slightly from?

Answer 2

the magnification stated

Question 3

Every microscope and every lens has to be…

Answer 3

calibrated individually using an eyepiece graticule and slide micrometer

Question 4

What is an eyepiece graticule?

Answer 4

a glass disc marked with a fine scale of 1 to 100

Question 5

What has no units and remains unchanged whichever objective lens is in place?

Answer 5

the scale

Question 6

The relative / proportionate size of the division increases with each…

Answer 6

increase in magnification

Question 7

What do you need to know in order to measure specimens?

Answer 7

what the divisions represent at the different magnifications

Question 8

What is calibrated using a stage micrometer?

Answer 8

the scale on the graticule at each magnification

Question 9

What is a stage micrometer?

Answer 9

a microscope slide with a very accurate scale in micrometres engraved on it

Question 10

The scale marked on the micrometer slide is usually…

Answer 10

100 divisions = 1mm

Question 11

1 division = …

Answer 11

1 micrometre

Question 12

What do you calibrate for each objective lens and how?

Answer 12

the eyepiece graticule scale seperaretly

Question 13

What happens once all three lenses are calibrated?

Answer 13

if you measure the same cell using the three different lenses you should get the same actual measurement each time

Question 14

Example: What happens first in calibrating a x4 objective lens?

Answer 14

put the stage micrometer in place and the eyepiece graticule in the eyepiece

Question 15

Example: What occurs after you put the stage micrometer and eyepiece graticule in place?

Answer 15

get the scale on the micrometer slide in clear focus

Question 16

Example: What happens after you get the scale on the micrometer slide in clear focus?

Answer 16

align the micrometer scale with the scale in the eyepiece

Question 17

Example: 30 divisions on the eyepiece graticule = …

Answer 17

10 divisions on the stage micrometer

Question 18

Example: 100 micrometer divisions =…

Answer 18

1mm

Question 19

Example: How much is each small division?

Answer 19

0.01mm

Question 20

Example: 30 graticule divisions = how many micrometre divisions?

Answer 20

10

Question 21

Example: 10 micrometre divisions = how many micrometres?

Answer 21

10 x 10 = 100 micrometres

Question 22

Example: 1 graticule division = …

Answer 22

number of eyepiece divisions / number of micrometres

Question 23

Example: 30 graticule divisions =…

Answer 23

100 micrometres so 1 graticule division = 100/30 = 3.33 micrometres –> the magnification factor

Question 24

Example: What do you have to do in order to use the magnification factor?

Answer 24

remove the stage micrometer and place a prepared slide on the stage

Question 25

Example: Measure the size of an object in…

Answer 25

graticule units

Question 26

Example: To find the actual size multiply the number of graticule…

Answer 26

units measured by the magnification factor to give you the length in micrometres

Question 27

Example: graticule divisions x…

Answer 27

magnification factor = measurement (micrometres)

Question 28

e.g., the diameter of a cell seen using the x4 objective lens measures 10 graticule divisions. Each graticule division = 3.33µm so the cell diameter…

Answer 28

= 10 x 3.33 = 33.3 µm