Metric measurement and microscopy

The metric system

• Standard system of measurement in sciences

• Length, weight, volume, tempreture

Metric units of length

Length: meter (m), centimeter (cm), millimeter (mm), micrometer (µm), nanometer (nm)

1m=100cm 1cm=10mm 1mm=1,000 µm 1µm=1,000nm

1m= 1×102cm= 1×103mm= 1×106 µm= 1×109nm

1nm= 1×10-3µm= 1×10-6mm= 1×10-7cm= 1×10-9m

Metric units of length

Metric units of length

What is your height?

Metric units of weight

• Weight: gram (g), milligram (mg)

1g=1,000mg= 1×103mg

1mg=0.001g= 1×10-3g

Metric units of weight

• Using scale to measure the weights of small objectives

Metric units of volume

• Volume: liter (l), milliliter (ml)

1l=1,000ml= 1×103ml

1ml=0.001l=1×10-3l

Meniscus Reading

•

Temperature scales

• Fahrenheit (F) & Celsius (C)

C= (F-32°)/ 1.8

F=1.8* C+32°

Microscopy

• Microscopes

　 Illumination source

MagnificationSliced section

imageThree dimension

image

Lightmicroscope

light　rayslower　(2000times)

regular　light　microscope stereo-microscope

Electronmicroscope

electron　beams

higher　(over500,000　times)

transmissionelectronmicroscope(TEM)

scanning　electronmicroscope　(SEM)　

Use of the compound light microscope

• Pick up the microscope carefully

• Never touch the lens with fingers.

• Use ONLY lens paper to clean the glass

• Don’t loss the key

The compound light microscope

• Two sets of lenses

—the ocular lenses

—the objective lenses

• The light only passes through clear portions, not opaque portions

• The objects must be small or thinly sliced sections

　Total magnification = magnification of the ocular lens × magnification of the objective lens

Identifying parts of microscope

Focusing the compound light microscope

• Always begin focusing with the lowest power objective

• Use coarse-adjustment knob ONLY with low-power objective

• Make sure the nosepiece is on the lowest power objective when done with the scope assignment

• Clean all slides, materials and work area

Field of view*

• Low-power objective has larger field of view

Depth of field*

• High-power objective has narrower depth of view

Microscopic Observations

• Prepared slides

• Onion

• Euglena

• Plant cell (root tip cell) • Gills of a fish