Microscopes

I. Types of MicroscopesA. Light Microscopes (2 types)

1. Compound (2D images) and dissecting (3D images)

2. Advantagesa. Can look at living thingsb. See in colorc. Requires simple preparationd. Fairly inexpensive

3. Disadvantagese. Specimens must be thin

Why?f. Limited magnification (~2,000X)g. Resolution is poor on higher magnifications

What is resolution and why is it poor on higher magnifications?

Draw and label the picture of a compound microscope on page 1070 and read Appendix D

There will be a quiz tomorrow on this picture and your lab!

B. Transmission & Scanning Electron Microscopes

1. Advantagesa. Greater magnification (scanning 100,000X

and transmission 200,000X)b. Scanning EM will provide 3-D view

Transmission EM Scanning EM

2. Disadvantagesa. Can only look at dead thingsb. Specimen preparation is time consuming

and expensivec. Objects appear black and whited. Very expensive

What type of microscope took this

picture?

What type of microscope took this picture?

What type of microscope was used to take both of

these pictures?

II. How to use the microscope

A. Carrying the microscope1. Always use 2 hands; one on the arm and

one on the base2. Do not tilt or swing the microscope because

the eyepiece may fall out

B. Setting up the microscope1. Place microscope on a flat, even surface,

about 3-5 inches from the edge of the table.

2. Unwrap cord and plug into the nearest outlet.

3. Use lens paper only to clean eyepiece and objectives of microscope.

4. Use paper towels to clean slides and any non-glass parts of the scope.

5. Place the microscope slide on the stage and secure it with the metal clips.

C. Using the microscope1. Always begin…

a) On lowest/scanning objective (4X)b)Eyepiece set to 10Xc) Diaphragm set to 1 or 2 (controls amount

of light)

d) Nosepiece lowered all the way down2. While looking through the eyepiece, move

the slide side to side until you locate a blurry object.

3. Use the coarse adjustment knob to center and focus on the blurry object.

4. Switch to next higher power objective; center and focus again. Adjust light if necessary.

5. If image isn’t clear enough, repeat steps 1- 4 going to the highest magnification.

Never use coarse adjustment (large knob) while on high power or you may break or scratch the lens.

6. Always switch back to scanning objective before removing the slide.

D. Putting away the microscope1. Make sure objective is set to scanning

(4x)2. Clean and dry stage, slide and cover-slip.3. Remove the plug from the socket (don’t

pull on the cord), loosely wrap up the cord around the base of the scope.

4. Lower the nosepiece, so it’s all the way down.

Magnification and Field of View