HOW TO MEASURE MICROSCOPIC OBJECTS A cluster of Escherichia coli bacteria magnified 10,000 times.

To put things in perspective, We need to consider some microscopic subjects and their size. Most people will have heard of an Amoeba. The typical size of this microscopic animal is 0.8 mm ( 8/10 of a millimeter) long by 0.4mm (4/10 of a millimetre) wide: just about visible to the naked eye! Measured in microns, the creature is quite large - 800 microns by 400 microns. It is a good reference size to consider smaller life-forms and objects against. Amoeba

Euglena ( protozoan) Typically 130 x 50 microns - much smaller than our large amoeba. It uses a whip like tail called a flagellum to propel itself through water at the rate of 20 to 200 microns per second. Compare this speed to its own body-length and than consider this to the speed of a Paramecium, another protozoan

Paramecium (another protozoan) "weighing-in" at 240 x 80 microns; the latter uses cilia (tiny hairs) to move through the water at 400 to 2000 microns per second.

Escherichia coli image is 8 micrometres wide. Bacteria Escherichia coli image is 8 micrometres wide. much smaller than any of the other forms and cells discussed so far, are typically between 1 micron to 10 microns in length; the latter being the length of the rod-shaped bacteria. If you look at the millimeter scale on your ruler, you can try and visualize 1000 bacteria lined up in a chain between the two marks indicating a millimeter width... or maybe just 8 Euglena "nose-to-tail".

What is the length of one onion cell??? How would you figure that out?? Onion Cells under Low Power (100x)

Now could you tell me how large the cell is???

To do this it will first be necessary to find the diameter of the low power field of view (FOV) PROCEDURE: Use the clear metric ruler (mm side) Be sure to line up the first mm mark with the left side of field

LP FOV = _____ mm 1.5

However, the mm is too large to measure microscopic objects, so you need to use the micrometer (micron) um 1 mm = 1,000 um 1 um = 1/1,000 mm or .001 mm

Convert your LP FOV in mm to um Use the metric sidewalk: K H D M d c m x x u When converting from mm to um, move the decimal point 3 places to the right LP FOV = _______ um 1500

HIGH POWER ( ) 400 Since you know the LP FOV, you just need to set up a proportion to calculate the HP FOV. LP Mag. 100 HP Mag. 400 HP FOV is LP FOV 1/4

So just divide the LP FOV by 4: 1500 / 4 = 375 HP FOV = _______ 375 um

GENERAL RULES FOR SWITCHING POWER: If you know the LP FOV, ________ to get HP FOV If you know the HP FOV, ________ to get LP FOV divide multiply

HP is 1/6 LP FOV for this microscope! QUESTION: If we switch microscopes and the new microscope has a HP magnification of 600X instead of 400X, how do you find the HP FOV? LP HP 100X 600X = = 1/6 HP is 1/6 LP FOV for this microscope!

Length of ameba = ________ Now you can measure microscopic objects in the HP FOV by comparing them to the diameter of the field. 1500 LP FOV DIAMETER = __________ um 1500 4 375 HP FOV DIAMETER = __________ um FORMULA: HP FOV Diameter = length of # times object object fits across 375 5 375 um HP FOV = ________ 75 um Length of ameba = ________

BACTERIA

SPIDER

MOSQUITO (FALSE COLOR)

FLY FOOT

RED FIRE ANT

MICROBES

POLLEN

Snowflake

Another snowflake

FLEA

SEM images – 3-D ANTARCTIC MITE (1500x)

Tip of a tatoo needle

Eyelash hair

Velcro hooks

Kitchen sponge with bacteria and fungus

Cat hair

Brown Recluse Spider

American Dog Tick Larvae

Crab Spider

Roundworm (in dogs)

Cattle hookworm

Cat tongue papillae

Cichlid fish gills

E. coli on surface of human skin and hair follicle

Human nose hair with mucus, pollen grain (green) and dead skin cells

Human tooth with accumulation of bacterial plaque (smooth areas) and calcified tartar (rough areas) on enamel surface.

Head louse

Staphylococcus aureus colony Staphylococcus aureus colony. MRSA strain (resistant to all penicillin-like antibiotics)

H1N1

Electron Photomicrographs supplied by: Dennis Kunkel Microscopy, Inc

PRACTICE PROBLEMS

1. How big is this Field of View in millimeters??? 3.5 mm

2. If the Field of View is 1.5 mm, what is the length of the paramecium in micrometers?

3. What is the length of one of the cells below in millimeters 3. What is the length of one of the cells below in millimeters? ___________ In micrometers? ___________ .5 mm 500 um

THE END