Biology I Lab instructions: Microscope

1. Microscope
• Micro (small)
• Scope (view)
Three common types:
1. Compound Light
2. Stereo
3. Electron (2 versions)

2. 1. Compound Light
• Most common
• 2 lenses focusing at the same time
1. Ocular
2. Objective
• 2D image
• High magnification through light
absorption

3. Parts of the microscope
Arm
Base

4. Term: Magnification
• Ratio of image size to actual size
• Ocular: 10X
(“X” means times; for example, the ocular
magnifies something 10 times)
• 4 objectives
– Scan: 4X
– Low Power: 10X
– High Power: 40X
– Oil immersion: 100x
• Multiply ocular x objective to get
overall magnification

5. Field of View
Amount of object you can see
• Decreases with increasing magnification

6. Depth of Focus
Thickness of specimen in focus at a given
magnification
• Decreases with increasing magnification
• Lab says to make your own slide-we will use a
prepared thread slide

7. Inversion Phenomenon
• Objects appear upside down and
backwards in the compound microscope
• We will use prepared letter e slides

8. 2. Stereomicroscope
• Used to get a better look at larger objects
• 3D image
• Specimen not mounted on a slide
• Low magnification
• Uses visible light through light scattering

9. 3. Electron Microscope
• Uses electron streams focused by
magnets to view specimens, not light
• 2 types
1. Scanning
2. Transmission

10. Scanning Electron Microscope
• 3D images
• 1,000-10,000x magnification
• Resolution of 5 nanometers
pollen
microscope

11. Transmission Electron Microscope
• 2D
• 10,000-100,000 magnification
mitochondria

12. Wet mount
• Way to create a simple slide
• Need a clean slide and a coverslip
• Procedure
– Place specimen on slide
– Add a drop of water
– Place coverslip over specimen at an angle to avoid air
bubbles
– Wipe away excess water
– View under microscope
• Today: pond water wet mount