Metric units are used to express the sizes of microbes.
The basic unit of length in the metric system is the meter (m); it is equivalent to 39.4 inches.
The sizes of bacteria and protozoa are usually expressed in terms of micrometers (µm). A micrometer is one-millionth of a meter
A typical spherical bacterium (coccus) is approximately 1 µm in diameter.
A typical rod-shaped bacterium (bacillus) is approximately 1 µm wide x 3 µm long.
The sizes of viruses are expressed in terms of nanometers (nm). A nanometer is equal to one billionth of a meter
Most of the viruses that cause human diseases range in size from 10 to 300 nm
One exception is Ebola virus, a cause of viral hemorrhagic fever. Ebola viruses can be as long as 1,000 nm (1 µm).
When using a microscope, the sizes of microorganisms are measured using an ocular micrometer
Answer
A) 0.001 or 1 x 10^-3
B) 1,000,000,000 or 1 x 10^9
C) 10,000,000,000 or 1x10^10
D) 0.01 or 1x10^-2
Microscope - it is the ultimate tool in studying microbiology
The human eye, a telescope, a pair of binoculars, a magnifying glass, and a microscope are various types of optical instruments.
A microscope is an optical instrument that is used to observe tiny objects, objects so small that they cannot be seen with the unaided human eye.
three main properties of the microscope:
Magnifying Power
Resolving Power
Contrast
Magnifying power - how much larger a given lens can make an image appear
Resolving power - how far apart two adjacent objects must be before a given lens shows them as discrete entities.
The resolving power of the unaided human eye is approximately 0.2 mm.
Contrast - ability needed to distinguish detail between adjacent objects.
Robert Hooke - he first used a microscope in 1667
Antonie van Leeuwenhoek - he used as single-lens microscope and observed "animacules" in 1675
Zaccharias Jansen - he invented the first compound microscope in 1600's
Joseph Jackson Lister - he developed a significantly better microscope in 1830
A simple microscope is one that contains only one magnifying lens.
A magnifying glass could be considered a simple microscope; when using a magnifying glass, images appear 3 to 20 times larger than the object’s actual size.
Leeuwenhoek’s simple microscopes had a maximum magnifying power of about x300 (about 300 times).
A compound microscope contains more than one magnifying lens.
Because visible light is the source of illumination, a compound microscope is also referred to as a compound light microscope.
The resolving power of a compound light microscope is approximately 0.2 µm (about 1,000 times better than the resolving power of the unaided human eye).
It is the wavelength of visible light (~0.45 µm) that limits the size of objects that can be seen.
Objects cannot be seen if they are smaller than half of the wavelength of visible light.
Today’s laboratory microscope contains two magnifying lens systems:
eyepiece or ocular lens
objective lens
ocular lens - it is usually x10
objective lens - x4, x10, x40, and x100 are the four most commonly used
The parts of a microscope can be categorized into:
Mechanical
Magnifying
Illuminating
Mechanical part - it is for support and adjustment
Magnifying part - it is for enlargement of the observed specimen
Illuminating part - It is for light provision
Mechanical parts are:
Base
Arm
Stage
Inclination Joint
Body tube
Draw tube
Revolving nosepiece
Dust shield
Coarse adjustment knob
fine adjustment knob
slide movement knobs
Base - holds various parts of the microscope including the light source.
Arm - connects the eyepiece and the objective lens