Journal Question #4
In the sponge lab experiment, what is the
dependent variable?
Types of Microscopes
1. Compound Light Microscope
- uses compound lenses and light
to magnify objects
- lenses bend or refract the light,
which makes the object beneath
them appear closer.
- specimens need to be translucent (allows light to pass through)
- magnification of up to a 1000x
2. Stereoscope
- also called a dissecting
microscope
- light source from top and
bottom => specimens can be
opaque
- microscope allows for binocular (two eyes) viewing of
larger specimens
2. Scanning Electron Microscope
- SEMs do not use light waves; they
use electrons to magnify objects up
to 100,000 times.
- specimens are coated with a metal,
usually gold.
- produces 3-D images of specimen
when electron reflect of metal coat
2. Transmission Electron Microscope
- also uses electrons, but instead of
scanning the surface (as with SEM's)
electrons are passed through very
thin specimens
- magnifies specimens up 200,000
times
- specimens are placed in parafilm
blocks and then sliced.
Parts of a Compound Microscope
Eyepiece
Body Tube
Revolving Nosepiece
Objective Lens
Stage Clips
Diaphragm
Light
Arm
Stage
Coarse Focus
Fine Focus
Base
Presentation in part from http://www.biologycorner.com/bio1/microscope.html
How to use a compound microscope
• Place the Slide on the
Microscope
• Use Stage Clips
• Click Nosepiece to the lowest
(shortest) setting
• Look into the Eyepiece
• Use the Coarse Focus
How to Use the High Power Objective
•
•
•
•
Follow steps to focus using low power
Click the nosepiece to the longest objective
Do NOT use the Coarse Focusing Knob
Use the Fine Focus Knob to bring the slide
Magnification
• To determine your magnification…you just
multiply the ocular lens by the objective lens
• Ocular 10x Objective 40x:10 x 40 = 400
So the object is 400 times “larger”
Objective Lens have
their magnification
written on them.
Ocular lenses usually magnifies by 10x
Magnification vs. Resolution
Magnification refers to the size of the image.
Resolution refers to how clear the image is.
Typically the more magnification the better
the resolution, but resolution tends to max
out first.
Caring for a Microscope
• Clean only with a soft cloth/tissue
• Make sure it’s on a flat surface
• Don’t bang it
• Carry it with 2 HANDS…one on the arm and
the other on the base