Microscopes

Light microscopes have been around for about 350 years.

Why invent the microscope?

• Most cells are too small to be seen with the naked eye.

• See the size chart in your textbook on page 51.

Who was the first person to use a microscope?

Robert Hooke,

from Britain, is credited

with viewing a thin

slice of cork wood in

1665.

This is a sketch of the cork cells, which Hooke drew in his notes.

These are actual cork cells as viewed through a microscope. He named them “cells,” because they reminded him of the small rooms in which monks lived in the monasteries of the time.

Ten years later, Anton von Leeuwenhoek, another pioneer in the field of microscopy, used a microscope to view water from a pond.

“Animalcules”

• Leeuwenhoek called the single celled organisms in the pond water animalcules. This means “tiny animals”.

• We now know that they are

single celled organisms.

Stentor

Leeuwenhoek also viewed “bee mouth parts and stings,” fungus, bacteria, and human louse.

What are all the parts of the microscope???

How do I set up a microscope?

1. Respect this very delicate and expensive tool!2. Use both hands when carrying the microscope.3. Clear a space for the microscope before you

go to get it.4. Place the microscope gently on the table or

desk.5. Never touch the lenses with your fingers!

How do I focus a microscope?

1. Start with the scanning objective. Turn to the objective marked 4x. Focus with the course adjustment knob (slowly) until you see an image. 2. Then focus more clearly with the fine adjustment knob.3. Then use the Low Power (marked 10x) objective to view at a slightly higher power. (Using only fine adjustment.)4. You may need to adjust the diaphragm for light to your viewing preference.5. Move to the High Power Lens (marked 40x), and use only fineadjustment to focus further.6. Use Oil Immersion only with INSTRUCTOR PERMISSION. This lens must be used with special oil, because it rests on the slide surface. It must also be cleaned with special lens cleaner in addition to lens paper, in order to completely remove the oil.

How much does each lens magnify?

4x/Scanning (used for centering an object and viewing gross structures.) 40x magnification10x/Low Power (also used for centering as well as viewing tissue and groups of cells.) 100x magnification40x/High Power (used for viewing cellular detail and some organelles.) 400x magnification100x/Oil Immersion (used for viewing bacteria and organelles.) 1000x magnification

How do I take care of the microscope?

1.Clean the lenses with the special lens paper, which is provided for you. 2. Do not take any parts off the microscope! 3. Use a slide cover, when viewing wet mounts.

How do I put away the microscope properly?

1. Turn off the power/light switch, and allow bulb to cool before moving.2. Clean lenses.3. Remove any slides from the stage.4. Turn the lenses to the lowest power objective. (10x)5. Wrap cord around base.6. Hold with both hands.7. Return microscope to storage area.8. Put dust cover on, if one is available.

These are some of the things Biologists can see with microscopes!

COOL!!!

Diatoms

Red Blood Cells

Onion Cells

Are there different kinds of microscopes?

1. Teaching microscope2. Dissecting Microscope3. Compound Microscope4. Darkfield Microscope5. Electron Microscope6. Stereo Microscope

This is an electron microscope,Which can magnify extremelysmall things to view in great detail!

Teaching Microscope

• Used so student and teacher can view the same object at the same time.

• Helpful in learning focusing, centering and measuring techniques.

Binocular Microscope

Monocular Microscope

Dissecting Microscope

• Used to view large and/or thick objects.

• Light may be provided from below, passing through it, or may be directed from above.

Compound (“Light”) Microscope• A light source

illuminates the object to be seen.

• As light passes through the object, the lens nearest the object, called the objective lens, produces an enlarged image of the object.

Darkfield Microscope

• The light does not pas directly through the specimen.

• Light is reflected off the specimen, making the specimen appear to be radiating light.

Comparison of compound and darkfield microscope images:

Electron Microscope

• Used to view objects that are even too small to be seen with a light microscope!

These are some electron micrographs, photostaken with an electron microscope. (See if you can guess what they are!)

Answers:

DNA strands Spider foot Spider spinerettes

More electron microscope pictures:

• The Golgi Apparatus

The head of a deer tick

Spirogyra (Protista-green algae) magnified 500x

A diatom magnified 15,000x

What is the difference between a regular microscope and an

electron microscope?• “Light” Microscopes

use illumination by light of many wavelengths.

• Magnify up to 2000x• Specimen may be

living or dead• Cost up to thousands

of dollars

• Electron Microscopes use electromagnetic lenses.

• Magnify up to 100,000x

• Specimen must be dead

• Cost hundreds of thousands of dollars

Stereo Microscope• Combines several images at different depths

of focus, in order to achieve a 3D effect.

With stereo imaging- entire object can be seen in focus.

Without stereo imaging only part ofthe object appears in focus

Magnification• Making an object appear larger than actual

size.

Resolving Power (“resolution”)• The measure of the clarity of an image.

Working Distance• The distance from the bottom of the

objective in use to the top of the slide.

Working Distance

Depth of Field• Demonstrates the three dimensional aspect

of specimens. Achieved by focusing on the specimen with the fine focus knob. Different parts of the specimen will be in focus as the fine focus knob is moved up and down.

Refractive Index• How much light is bent as it passes through

different substances, such as air, water, or oil.

Oil versus air light refraction

Notice how light is bent hereas it passes through air.

But the light does not bend as it passes through oil!

Parfocal• If an object is in focus at low power, it will

also be in focus when the objective is switched to high power.

Parcentration• If an object is centered when viewed at low

power, then it will also be centered when the objective is switched to high power.

Notice how the microchip is centered at top right and bottom left.

This image is NOT parcentered!

Eyepiece Micrometer • The tiny ruler visible in the viewing field of

some microscopes.

Measurement of a Specimen

Measurement of a Specimen

Measurement of a Specimen

Light Microscopes work by concentrating light with a series of mirrors.

Transmission Electron Microscope (TEM)

These work by passing electrons through the specimen to a photographic plate and the image is created. The specimen is thinly sliced and stained with electrons. The operator uses fluorescent screens to view the object.

TEM

(TEM is able to magnify slightly better than the SEM)

The Scanning Electron Microscope (SEM)

The SEM bombards the specimen with electrons, which do Not pass through it. Secondary electrons are emitted by this process, and a 3D image is photographed. (Both electron microscopes can magnify an object up to 100,000 times.)

Some pictures from the TEM and SEM:

Feather Fly foot

Butterfly Wing Scales

From an electron micrograph photo contest, it’s entitled “chat.”

DNA

Termite Spider

Centrifugation

Another way of studying cells is to centrifuge them. The organelles are separated by “ultracentrifugation” using a density gradient. The unique density (mass) of each organelle type allows them to settle at different levels in the test tube. This separation takes several hours at 40,000 revolutions per minute. The function of each type of organelle can be studied later as well.

Cell Staining techniques have improved our ability to understand cells and organelles.

Gram – stain

Gram + stain

Fluorescent stains

Some microscopes from the microscope museum.

Now lets get ready to use this newfound knowledge!!!

I hope you paid attention!

The End