Introduction to Microscopes! Now Seeing IS Believing!

A Brief History

Simple Glass Magnifiers More than 500 years ago. In 1600s, this “simple microscope” allowed scientists to see cells and bacteria Problem: not enough magnification

First Compound Microscope Developed at the beginning of the 1600's, by the Janssen brothers and Galileo Problem: images were blurred and had colored halos

Simple Compound Microscope Invented in 1660s Problem: all images had red or blue “halos” around them

Even better! 1700 and 1800s – great improvement in microscopes Usually made of brass (expensive) Had a tripod for support

Modern Compound Microscope Definition of a Compound Microscope : an instrument for magnifying small objects, consisting of a lens of short focal length for forming an image that is further magnified by a second lens of longer focal length Compare

Fancy! Better images More magnification Better lighting Easier to use Now everyone, at one time or another, has looked through a microscope

How Does It Work? A microscope works very much like a telescope. A telescope must gather light from a dim, far away object. So, it needs a large objective lens to gather as much light as possible and a long body to bring the image into focus.

How Does It Work? Unlike a telescope, a microscope must gather light from a tiny specimen that is close-by. So the microscope does not need a large objective lens. Instead, the objective lens of a microscope is small. Then the image is again magnified by a second lens, called an eyepiece, as it is brought to your eye.

Parts of a Compound Microscope So EASY a KID could use it!

← Base The bottom of the microscope, used for support Hold this part with one hand when carrying a microscope ←

Mirror Reflects the light so the specimen is easier to see ←

← Stage The flat platform where you place your slides. It has a hole in it so light can shine through ←

Clip Shiny clips on the top of the stage Holds a slide in place ←

← Arm Supports the tube and connects it to the base The part you hold when you carry the microscope ←

→ Coarse Adjustment Large, round knob on the side of the microscope Either moves the stage or the top part of the microscope up and down →

→ Fine Adjustment Small, round knob on the side of the microscope Used to fine tune the focus after using the coarse adjustment knob. →

Eyepiece → The lens at the top that you look through. 10X power

Body Tube The long tube that holds the eyepiece and connects the objective →

Nosepiece Rotating part of the microscope at the bottom of the body tube. It holds the objective lenses ←

→ High Power Objective The longest objective lens The highest magnification 40X lens (40X x 10X = 400X magnification) →

← Low Power Objective The shortest objective lens The lowest magnification 4X lens (4X x 10X = 40X magnification) ←

← Mid Power Objective The medium length objective lens The medium magnification 10X lens (10X x 10X = 100X magnification) ←

Diaphragm Controls the amount of light going through the hole in the stage →

Pop Quiz What two parts should you hold when you carry a microscope? Base & Arm Where do you put a slide? On the Stage To focus, what knob do you turn first? Second? First, Coarse Adjustment Second, Fine Adjustment ← ← ← → ←

Test Your Skills . . . Arm Body Tube Stage Clip Base Coarse Adjustment Fine Adjustment

Test Your Skills High Power Objective Low Power Objective Mirror Eyepiece Nosepiece Diaphragm

http://www.udel.edu/biology/ketcham/microscope/testFLV8.html http://www.wisc-online.com/objects/index_tj.asp?objID=BIO905