The First Microscopes

Antony Van Leeuwenhoek (1632-1723), is given credit as the “Father of Microscopy”.

He developed simple microscopes that used only one lens.

The First Compound MicroscopeThis microscope was built by Zacharias Janssen and his father Hans.

It is a compound microscope because it uses two lenses.

The Modern Classroom Microscope

The eyepiece magnifies the image, usually 10X.

If dirty, clean with lens paper only!

The body tube maintains the correct distance between the eyepiece and the objectives. This is usually about 25 cm, the normal distance for reading and viewing objects with the naked eye.

The scanning objective (shortest) will magnify an object 4X.

The low-power objective will magnify an object 10X.

The high-power objective will magnify an object 40X.

Keep each small lens clean by using lens paper.

The Revolving Nosepiece holds the objectives and can be turned to change from one objective to another.

Using the nosepiece will help keep oils on fingers from getting on the objective lenses.

The light source provides light for viewing the image.

There will be a switch located on the base that will turn it on.

The diaphragm, controls the amount of light that is allowed to pass through the object being viewed.

You will want more light for objects that are thick or pigmented and less light for objects that are thin and have little pigment.

The Arm supports the body tube.

A person should also hold onto the arm when transporting the microscope.

The base supports the microscope.

Make sure that one hand holds the base as the microscope is being transported.

The stage supports the slide.

It also moves up and down so that the image will come into focus.

The stage clips secure the slide in position for viewing.

Notice that your microscope probably has a spring loaded clip.

Always gently secure the slide with this clip so that the glass slides do not chip.

The Stage Controls will move the stage clips and slide so that the slide is positioned properly below the objective.

The Coarse Adjustment Knob moves the stage up and down in large increments to allow better positioning and focusing of the objective lens.

This knob is mainly turned when using the scanning objective.

The Fine Adjustment Knob moves the stage slightly to bring the image into sharp focus

The 4 “golden rules”

• Always carry the microscope with two hands – one on the arm and one on the base

• Always store it with the lowest power objective clicked into place

• Always store it with the stage all the way down

• Always wrap the cord around the base

What’s my total magnification?

To calculate the total power of magnification, multiply the power of the ocular lens by the power of the objective.

What are the powers of magnification for each of the objectives we have on

our microscopes?

Scanning Objective =10 x 4 = 40X

Low Power Objective = 10 x 10 = 100X

High Power Objective = 10 x 40 = 400X

Comparing Powers of Magnification

We can see better details with the higher powers of magnification, but we cannot see as much of the image.

Which of these images would be viewed at a

higher power of magnification?

Resolving Power

The smallest separation at which two separate objects can be distinguished.

How to make a wet-mount slide …

1 – Get a clean slide and coverslip from your teacher.

2 – Place ONE drop of water in the middle of the slide. Don’t use too much or the water will run off the edge and make a mess!

3 – Place the edge of the cover slip on one side of the water drop.

5 – Place the slide on the stage and view it first with the scanning objective. Once you see the image, you can rotate the nosepiece to view the slide with the different objectives.

4 - Slowly lower the cover slip on top of the drop.

Cover Slip

Lower slowly

Electron Microscopes

uses electrons to "illuminate" an object. Electrons have a much smaller wavelength than light, so they can resolve much smaller structures.

-can magnify 100,000 times or more

-images are viewed on a monitor

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