Today is Wednesday,October 7th, 2015

Pre-Class:Write down three facts you know about microscopes. I

will call on each of you for one of them.

Please get a SMALL paper towel for your pair and take a worksheet from the turn-in box.

In This Lesson:Unit 2

Microscopes(Lesson 1 of 5)

Today’s Agenda

• Challenge Questions• Unit 2 Pre-Test• History of microscopes• Virtual microscopes• Real microscopes• Seeing atoms• Painting with fly hair

• Where is this in my book?– Academic: P. 169 and following…– Honors: P. 52 and following…

By the end of this lesson…

• You should be able to properly use a microscope and describe its parts and their functions.

• You should be able to distinguish between types of microscopes, including their advantages and disadvantages.

IMPORTANT NOTE

• Some of the information we need to learn about microscopes will be discussed when we do the Microscope Lab.– If you’re absent that day, make sure you consult

the “Theoretical Data” file and the file called “Lab – Microscope – Information” on my website (Assignments section).

History of Microscopes

• In the beginning, around 1284, eyeglasses were invented.

http://www.spectaclesblog.com/wp-content/uploads/2009/09/spectacles-in-the-scriptorium-1352.bmp

I still couldn’t see the Bubonic

Plague coming.

History of Microscopes

• Around 1590, two Dutch guys (Zacharias Janssen and his son Hans Janssen) put a bunch of lenses together in a tube and noticed that they brought small objects into focus.

• Early light microscope!– Janssen also claimed credit for

inventing the telescope, but that usually goes to Hans Lippershey.

http://www.microscopy-uk.org.uk/mag/imgjan07/Fig004s.jpghttp://micro.magnet.fsu.edu/optics/timeline/people/antiqueimages/lippershey.jpg

http://www.history-of-the-microscope.org/images/Zacharias-Jansen.jpg

Light Microscopes

• Light microscopes, like the ones we’re using, require light to pass through the sample and into the eyepiece.

• Relatively inexpensive.• Can see down to around the level of cell parts

– maybe a little smaller.• Can use living things.• Sometimes called optical microscopes.

Then a lot of time passed…

• Until we got to the early 1900s. The scanning electron microscope was invented.– Uses a beam of electrons to create images!

• It’s big, it’s bulky, it’s expensive, but it’s super-powerful. Does not allow for living specimens.– Samples must sometimes be coated in gold!

• Does not require light to pass through an object.• Can view objects about the size of the diameter

of an atom.

Types of Microscopes

• Scanning Electron Microscope:

http://img.directindustry.com/images_di/photo-g/schottky-emission-scanning-electron-microscope-sesem-237074.jpg

Electron Microscope Images

http://blog.lib.umn.edu/willow/bioarts/exhibition-ideas/

Electron Microscope Images

http://blog.lib.umn.edu/willow/bioarts/exhibition-ideas/

Electron Microscope Images

http://www.photosfan.com/electron-microscope/

Trichinosis spiralis(microscopic animal parasite from undercooked meat)

Electron Microscope Images

http://www.photosfan.com/electron-microscope/

How “Far” Can They See?

• Let’s compare.• Scale of the Universe

Scanning Tunneling Microscope

• Invented in 1981.• Currently the most powerful microscope

available.• Can see three-dimensional objects at the

atomic level.• Video!

Willard Wigan

• And now for something a bit more…unusual…having to do with microscopes.

• This is real.

The Microscope Checklist

• So, let’s talk about the parts of a microscope.• Head to your lab tables with your worksheets

and notebooks.• Two people from each table should get

computers.

Parts of a Microscope

Eyepiece

Low-Power(Scanning) Objective

Mid-Power Objective

High-Power Objective

Stage Clips

Stage

Light

Base

Fine Focus Knob

Coarse Focus Knob

Diaphragm/Iris

Arm1.

2.

3.

4. 5.

6.

7.

8.

9.

10.

11.

12.

Parts of a Microscope

• Arm– Supports the stage, eyepiece, and objectives.

• Base– Supports the scope.

• Objectives and Eyepiece– Magnify the sample.

• Stage and Stage Clips– Hold the slide.

Parts of a Microscope

• Coarse Focus– Focuses the image on low power.

• Fine Focus– Focuses the image on higher powers.

• Diaphragm/Iris– Controls the amount of light entering the

objective.• Light– Provides the uh…light.

Meet Your Microscope

• Follow this path on your microscope:– When using a light microscope, light comes up

from the source through the diaphragm.– It passes through the slide and the object

mounted on the slide.– It goes into the objective lens, up the tube and

through the eyepiece lens, finally going into your eye.

Handling Your Microscope

• First, only handle the scope by the base and arm.– One hand on the arm, the other underneath, as

though you’re carrying a giant teacup.– See demonstration!– Give it a shot yourself. Make sure everyone at

your table has an opportunity to pick up and set down the scope.

Meet Your Microscope

• On low power, the light entering the objective is magnified how many times?– 4x

• However, it has to pass through another lens – the eyepiece!– The eyepiece magnifies 10x.

• Therefore, to find total magnification, multiply eyepiece magnification by objective magnification.– What are the possible magnifications here?– ALWAYS include magnification with any sketches you

draw. It’s like including units with measurements.

Virtual Microscope

• Now we’re going to do a little practice on a virtual microscope.

• First, log into Quia and complete the Unit 2 Pre-Test as a pair.

• When you’re finished, launch the following website:– Virtual Microscope

http://www.udel.edu/biology/ketcham/microscope/scope.html

• Close the tour and turn on the checklist.• View the letter “e” on the microscope correctly,

then call me over.

Virtual Microscope

• http://www.udel.edu/biology/ketcham/microscope/scope.html– Or Supporting Documents – called “Virtual Microscope.”

• Close the tour.• Select the slide with the “Letter e” mounted on it.• Select “Checklist” from the upper left corner.• Complete each of the steps. You will need to figure

out how to do some of this on your own.– Consider it a scavenger hunt!

• When you are finished, show me your results, turn off your computer, and put it away.

Closure

• Using a whiteboard, answer the following questions:– Rank the microscopes in terms of increasing

magnification power:• Light Microscope, SEM, STM

– What is the total magnification on your high-power objective? How did you calculate it?• (show the equation)

Closure

• TED: Dee Breger – Visualizing Hidden Worlds Inside Your Body