Topic 2: A Microscopic world

Our eyesight limits our understanding of our world People with good eyesight can see only clear, defined images of things that are 0.1mm or larger

What is a microscope? An instrument for viewing objects that are too small to be seen easily by the naked eye

History of the Microscope 1000 Reading stone Curved outwards Enlarged print 1284 1st wearable eye glasses

1590 Hans & Zacharias Janssen experimented with multiple lenses placed in a long tube Microscope Objects viewed in front of the tube appeared greatly enlarged 20X magnification

1665 Robert Hooke Viewed a piece of cork through a microscope lens and noticed small “rooms” Cells

1674 New methods that provided magnifications up to 270X Anton van Leekuwenhoek Examined blood, yeast, insects through a microscope 1st person to describe bacteria

Magnifies up to 1 000 000 x! 1930s Phase-contrast microscope Allowed for the study of colorless and transparent materials Electron microscope Max Knoll & Ernst Ruska Uses electrons rather than visible light Possible to view objects as small as the diameter of an atom Magnifies up to 1 000 000 x!

Pollen Surface of a flower petal (1500x) Eye of a fly Hydrothermal worm

Scanning tunneling microscope Gives 3D profiles of the surface of objects down to the atomic level Roughness, defects

Workings of a Compound Microscope Source of light Light waves enter a glass objective lens and are bent Bending enlarges the image Light waves enter an ocular lens and are bent

The power of the microscope depends on how much each lens bends the light Ocular Lens = 10X Objective Lenses = 4X, 10X, 40X

Parts of the microscope Label the parts of the microscope on the diagram provided Determine the function of each part

Part Function Ocular lens (eye piece) Arm Base Coarse Adjustment Knob Fine Adjustment Knob

Part Function Revolving Nosepiece Objective Lenses Stage Stage Clips Diaphragm Lamp

To view specimen: 1. Turn on lamp 2. Center specimen in field of view 3. Focus using lowest-power objective lens (4X) Coarse adjustment knob Fine adjustment knob 4. Switch to medium-power (10X) 5. Focus using fine adjustment knob only

Keep both eyes open Coarse adjustment knob Use only on the lowest-power lens Fine-adjustment knob Use with any objective lens Revolving nosepiece Listen for a click when turning the lens

Ocular & objective lenses Avoid touching the lenses Clean with lens-paper Diaphragm Adjust to intensify or dim light for better viewing

Laboratory Assignment: A Microscopic World