Basic Laboratory Skills: Making Microscopic

Measurements : Lab 2d

MICROSCOPIC MEASUREMENT AND DRAWING

Word of the Day:

Magnification: the process of enlarging something

How big is a cell?

• http://www.cellsalive.com/howbig.htm

How can we determine the size of a specimen under the

microscope?• Most accurate:

– Micrometer• Ruler• Built into ocular

• Alternative:– Estimate using

the technique

we will do today!

Our Method - Low Power

• Make a wet-mount of a piece of 1-mm graph paper (10mm2)

• Count how many millimeters across appear in your field of view in low power (40X - with eyepiece)– Convert to micrometers– How many micrometers in a millimeter?– Record this in results!

Making Microscope Measurements

1 Box = 2 mm

Total view = 2 boxes =4 mm across=4000 μm

40X

Field of Vision Sizes

• Field of visions for higher powers are based off of the 40X field

• 100X is 2.5 times smaller then 40X

• 400X is 10 times smaller then 40X

40X

100X 400X

2.5 times smaller

10 times smaller

Fields of Vision• 40X = 2 boxes = 4 mm 4000 μm

• 100X = 2 boxes/2.5 = .8 boxes = 1.6 mm 1600 μm

• 400X = 2 boxes/10 = .2 boxes = 0.4 mm 400 μm

*All measurement are for width across the middle*

Field of Vision at High Magnifications

• You know that…– The field of vision is

~400 μm wide

• You estimate that…– The cell takes up

about 1/3 of the width

• You can calculate that…– The cell is about

133.3 μm– 400*1/3 = 133.3 μm

400X

Procedure1. Make a wet mount of mm grid graph paper. 2. Count how many 1-mm square go across

the diameter of the low power field.3. Convert the diameter measurement from

mm to µm.1 mm = 1000 µm

4. Create a data table and record the size of the low power field in both mm and µm

mm µm

40x

100x

400x

Procedure (cont.)5. Do the division (do NOT measure!) to calculate the

sizes of the medium and high power fields.

40X

100X 400X

10x smaller2.5 x smaller

6. Report the values in both mm and µm in data table

Next!!!!!!!

• Choose a slide and draw your organism– Use details– Use shading– List power drawn under– Make large

Example

• Paramecium– 400X