Microscopes Viewing the Unseen World

Microscopes Devices that produce magnified images of structures that are too small to see with the unaided eye.

Types of Microscopes - Compound Microscopes - Stereo or Dissecting Microscopes - Electron Microscopes

The Compound Microscope - Produces a magnified image by focusing visible light rays. -Uses 2 lenses -Can observe living or nonliving specimens. -Magnification is limited by visible light.

The Stereo or Dissecting Microscope The Stereo Microscope is used when viewing large specimens. A 3-D image is viewed. Light does not pass through object but magnifies the surface.

The Electron Microscope -This type of microscope focuses beams of electrons to magnify an image. - It magnifies 1000X or more than a compound light microscope. -It cannot be used to study live specimens because they must be dried and in a vacuum inside the microscope

Quick Questions: Q: What are 3 types of microscopes? A: Compound, Dissecting (stereo) and electron Q: Which allows light to pass through a specimen? A: Compound microscope Q: Which does not allow light to pass through a specimen? A: Dissecting or stereo microscope Q: Which uses electrons and a computer to interpret the results? A: electron microscope

3 types of electron microscopes Scanning Electron Microscope – SEM Produce a realistic, 3D image- but only the surface can be observed. Magnifies 60,000x Transmission Electron Microscope – TEM 2D images used to study details of cells. Magnifies 100,000+ X Scanning Tunneling Microscope – STM magnifies so much that scientists can see atoms on the surface of objects. Magnifies 100 million X

The Compound Microscope Essential Questions: What are the parts of a compound microscope, and what function does each serve?

The Eyepiece- (Ocular) Part of the microscope you hold your eye up to and look through. The eyepiece contains a magnifying lens and magnifies 10X. Eyepiece (Ocular) The lens system in microscope that is nearest your eye. It magnifies the image formed by the objective.

360 –Degree Rotating Head The head is able to rotate 360 degrees without moving the base of the microscope and disturbing the focus.

The Revolving Nosepiece Holds three or four objective lenses. The nosepiece can be rotated to change the objective lens being used. Each objective lens has different level of magnification

The Objectives Primary magnification of the object being viewed. Inscribed on each objective is the magnification of the lens. 4X – scanning lens 10X – low power 40X – high power Note: We will NOT be using 100X objective lenses in this class

Total Magnification To find total magnification MULTIPLY the number on the objective lens times the number on the eyepiece.

Quick Question: Q: What would be the total magnification if I was looking through the ocular lens and using the scanning lens (4X)? A: 10 X 4 = 40 Q: What would be the total magnification if I was looking through the ocular lens and using the low power lens (10X)? A: 10 X 10 = 100 Q: What would be the total magnification if I was looking through the ocular lens and using the high power lens? A: 10 X 40 = 400

The Arm The main vertical section supporting a microscope One hand is ALWAYS placed on this when carrying the microscope!

The Stage Platform that supports the slide This is where you place a sample that you are trying to view It should ALWAYS be lowered completely when placing a sample on it

The Stageclips Holds a slide in place as it is being observed.

The Diaphragm The Diaphragm is a disc located under the stage. It contains 5 or 6 holes to control the amount of light that passes up through the specimen This is the most underused piece of equipment on the whole thing. Too much light washes out the details of the specimen

Quick Question: Q: What is the most underused piece of equipment on the microscope? A: The Diaphragms Q: What does it do? A: regulates the amount of light being passed through a specimen Q: If you use it wrong, what happens? A: They specimen gets “ washed out ” and you loose the fine details such as organelles, cilia, and flagellum

The Illuminator (Light Source) Light source for the Microscope

The Base The Base supports the microscope. This is where your other hand goes when carrying a microscope You hold the base with one hand and the arm with the other hand.

Quick Question: Q: What is the ONLY way that you will EVER carry a microscope in my class? A: With BOTH hands; one on the arm, the other under the base

Focusing Knobs The Course Adjustment Knob- larger and is used to focus the image. –This is what you use to lower the stage prior to placing a specimen on it –Only used with the scanning lens The Fine Adjustment Knob- smaller and is used to sharpen the image. –Fine tuning once you get close

Magnification: The Microscope ’ s job is to enlarge images Unfortunately, as we increase magnification, we decrease Resolution, which is how clear something looks

Magnification vs. Resolution Magnification is the process of enlarging an image Resolution the level of clarity or detail that is evident Example: Take a picture on your cell phone, then blow it up on your computer screen What happens?

Now for some Practice Get with a lab partner at one of the stations around the room. –ALWAYS make sure that chord is unwound from around the microscope, and plugged into an outlet. –Turn the power switch ON when using, and OFF when you are done!

Preparing a sample – do as I do Take a glass slide from the bench Place a sample on the slide using a pair of forceps Place a SINGLE drop of water on the sample Take a cover slip from the bench, and DO NOT touch anything except the sides (they smudge easily) Place the cover slip at a 30° angle to the sample on the slide, and gently drop it onto the drop of water over the sample

Next… Lower the Stage ALL THE WAY using the Coarse Adjustment knob. Place the sample on the Stage, under the stage clips. Make sure that the Revolving Nosepiece is turned to the scanning lens (4X)

Now for the finishing touches… Look through the Ocular Lens, and SLOWLY raise the Stage by using the Coarse Adjustment Knob until you start to see an image As soon as you see SOMETHING, switch to the Fine Adjustment Knob, and continue raising the Stage until your image is in view Move the slide gently to center the image

Once your image is in view… Rotate the Revolving Nose Piece to the next higher lens (Low power; 10X) and make sure your image is still centered Use the Fine Adjustment Knob ONLY from now on Refocus the image, and Make sure it is centered. What do you notice about your movement of the slide versus how the image moves?

Last Time… Now rotate your revolving nosepiece again to the high power lens (40X), and focus one more time using the fine focus knob ONLY! What do you see? Now adjust the diaphragm while looking through the ocular lens and see what happens to the details of your sample Stick with the one that has the greatest detail

The finishing touches… In many cases you will be asked to draw or document what you view under a microscope This is how it is to be done, NO OTHER WAY!

Draw a large circle on a sheet of paper, if there isn ’ t already one given to you 1.Circle 2.Title the top with what the image is 3.Record the magnification 4.Diagram what you see at the HIGHEST MAGNIFICATION you get clearly 1.You may need to do different sketches at different magnifications for the same sample at times Letter e 400 X

Now it ’ s your time to try… Now that you have the image and it is recorded, pick a partner to go first That partner is to select a sample, prepare a slide, and place it on the microscope. Next, mis-adjust several settings WITHOUT causing damage to the microscope Now stand back and watch as your partner fixes it, and gets the image into the correct magnification and focus, and draws it on their practice sheet. Once they have it correct, they may select a sample, prepare it, and mis-adjust the scope. Continue until both partners are comfortable with finding images in the microscope.