2  Use of the Microscope

2.1 Objectives

  • Identify the parts of the microscope and list their functions

  • Demonstrate proper use, care, and transport of the microscope

  • Define total magnification, resolution, parfocal, field diameter, depth of field, and working distance

  • Apply microscopy skills to view histology slides

  • Explain why field of view decreases with magnification

2.2 Terms to Learn

Arm
Neck
Body
Base
Ocular lens
Objective lens
Revolving nosepiece (turret)
Coarse and fine focus knobs
Mechanical stage
Mechanical stage knobs
Light source
Iris diaphragm
Condenser

2.3 Prelab Activity 2.1

2.3.1 Identification of Microscope Parts

  1. Ocular lens

  2. Head

  3. Revolving nosepiece (turret)

  4. Objective lenses

  5. Mechanical stage

  6. Arm

  7. Coarse focus knob

  8. Fine focus knob

  9. Light source (illuminator)

  10. Base

2.4 Prelab Activity 2.2

2.4.1 Matching: Microscope Parts and Definitions

Microscope Part Definition Letter
Condenser j
Revolving Turret g
Mechanical stage q
Ocular lens e
Power switch p
Iris diaphragm k
Arm d
Depth of field o
Fine focus i
X-Y stage controls l
Light source a
Total magnification m
Head b
Base c
Objective lens f
Course focus h
Field of view n

2.5 Lab Activity 2.1 β€” Magnification

2.5.1 Lens Magnification Table

Lens Ocular (10X) Objective Total Magnification
Scanning 10X 4X 40X
Low power 10X 10X 100X
High power 10X 40X 400X
Oil immersion 10X 100X 1000X

2.6 Measuring the Field of View

2.6.1 Measured Field of View

Scanning lens (4X)
4.5 mm
4500 Β΅m

Low power lens (10X)
1.8 mm
1800 Β΅m

2.6.2 Calculated Field of View

High power lens (40X)
0.45 mm
450 Β΅m

Oil immersion lens (100X)
0.18 mm
180 Β΅m

2.7 Focusing Exercises

2.7.1 Letter β€œe” Exercise

  • The image through the microscope is upside down and reversed

  • The magnified β€œe” appears inverted compared to the unaided view

2.7.2 Depth of Field β€” Colored Threads

  • More adjustment is required at higher magnification

  • Under high power, not all threads are in focus at once

  • This shows that depth of field decreases as magnification increases

2.8 Examining Tissues

Slides were examined at:

  • 40X

  • 100X

  • 400X

2.9 Troubleshooting Summary

  • Dark image β†’ adjust diaphragm and rheostat

  • Cannot focus β†’ return to scanning lens and refocus

  • Spots in field β†’ clean lenses

  • Half‑moon view β†’ objective not fully engaged

  • Eyestrain β†’ adjust ocular distance and light intensity

2.10 Chapter 2 β€” Microscopy Glossary

Term Definition
binocular microscope with two eyepieces
brightfield microscope compound microscope with dark image on light background
coarse focus knob used for large focus adjustments
condenser lens focuses light onto specimen
fine focus knob used for small focus adjustments
fixation attaching specimen to slide
illuminator light source
lens refracts and focuses light
magnification enlargement of image
monocular microscope microscope with one eyepiece
objective lenses lenses closest to specimen
ocular lens eyepiece
oil immersion lens used with immersion oil
refraction bending of light
resolution ability to distinguish two points
rotating nosepiece holds objective lenses
stage platform holding the slide
total magnification ocular Γ— objective
wet mount specimen in liquid
x‑y stage knobs move slide horizontally/vertically

βœ… End of Chapter 2