horizontal rule

Objectives

The Student should be able to:

  1. Identify, locate and describe the function of the major parts of the compound light microscope.

  2. Identify, locate and describe the function of the major parts of a stereo (dissecting) microscope.

  3. Properly carry, place, prepare, and use the microscope in the laboratory setting

  4. Use the correct protocol for view a slide with the microscope.

  5. Determine the magnification of oculars, objectives, and total magnification of the microscope.

  6. Properly make and view a "wet mount" slide and a prepared slide with the microscope.

  7. Understand the properties of magnifying lenses when used separately or in conjunction with each other.

  8. Sketch material as it appears under the microscope.

horizontal rule

Introduction

The development of the microscope from a simple magnifying lens to a compound  light microscope and then to the electron microscope is interesting and important to biologists because much of the living world is microscopic or portions can be taken and view microscopically. The smallest living unit is the cell, and most cells are invisible to the naked eye, hence the microscope, became a valuable "tool" for the biologist. He was now able to view much of the living world that was invisible to man for eons. The earliest "microscopes" are credited to Antony von Leeuwenhoek (1632-1723) and Robert Hooke (1635-1703). Click on their name to find out information about these two men. Prior to the developments of Leeuwenhoek and Hooke, little was known about the "microlife" that inhabits the planet.

You will be using two basic types of microscopes in lab. They are the compound light microscope and the stereo (dissecting) microscope. You will also be using hand-held magnifiers (glasses and loupes) to the enhance viewing of many items.

The compound light microscope uses a system of lenses (2) to increase the magnification of objects. The objects must be thin, so light passes through them, and mounted on a surface, such as glass. The lens system is formed by the ocular lenses (sometimes called the eyepieces) and the objective lenses. Both types of microscopes you use are binocular in nature, meaning they have two ocular lenses that you look through. They are also parfocal, meaning if they are in focus at one objective setting (i.e. low power) and you change the objective setting (i.e. high dry) then they will be in focus at the new setting.

horizontal rule

Pre-lab Activity

The pre-lab activity for this lab requires you to become familiar with the parts and functions of the compound microscope and acquaints you with the operational protocol for transporting, setting up and using the microscope. Remember the microscope is a "tool" for viewing small forms of life, so the operation of it should become "second nature". You will also collect information about the types of microscopes and their specialized use in microscopy.

Click on the photographs below to obtain information about the microscopes that you will use in lab.

         

           

horizontal rule

Pre-lab Questions (html version)         Pre-lab  Questions (Word version)

horizontal rule

The Laboratory Activities and Data Collection

Lab Activity #1 - Familiarization

Materials:

bullet

Compound light microscope

bullet

Printout of the compound light microscope picture

bullet

Printout of the protocol for using the compound light microscope

Procedures: (Your instructor will provide an overview and assistance for this procedure)

  1. Procure a microscope from the prep room and properly transport it to your lab station.

  2. Set up the microscope as describe in the pre-lab activity.

  3. Familiarize yourself with the basic parts to the microscope (picture).

  4. Do a "dry run" of the protocol for using the compound light microscope.

horizontal rule

Lab Activity #2 - Field of View and Depth of Field

Materials:

bullet

Compound light microscope

bullet

"e" slide

bullet

"thread" slide

Procedures: (Your instructor will provide an overview and assistance for this procedure)

  1. Obtain a prepared slide ("e" or "thread") depending on which part of this procedure you a doing)

  2. Make sure the 4x objective is in position

  3. pull the stage clip to the open position and hold it open

  4. Place the "e" slide in the mechanical stage, and carefully return the stage clip to the closed position so it can hold the slide.

  5. Following the procedures for using and focusing the compound light microscope, view the "e" at 4x, 10x, and 40x. DO NOT USE 100X (OIL IMMERSION).

  6. Notice that the "e" is upside down. As you progress to higher power objectives the "e" will occupy more of the field.

  7. Answer the post-lab questions related to this activity.

  8. When you have finished with the "e" slide return it.

  9. Repeat the above procedure (Steps 1 - 7) using the "thread" slide. ONLY USE 4X AND 10X OBJECTIVES FOR THIS. DO NOT USE 40X OR 100X OBJECTIVES.

  10. At 10x, find, focus and center the point where the thread cross each other.

  11. While viewing the crossed threads Carefully turn the fine adjustment knob slowly toward you until the crossing area is slightly blurred.

  12. Now carefully turn the fine adjustment knob away from you and notice which thread comes into sharp focus. This is the thread on top. Continue turning the fine adjustment knob until the next color comes into sharp focus, this is the one in the middle. By default the last color is on the bottom. Focus on this one.

  13. Determine, at the point where they cross, which color thread is on top and which one is on the bottom.

  14. Answer the post-lab questions related to this activity.

  15. When you have finished with the "thread" slide return it.

horizontal rule

Lab Activity #3 -"Wet mount" Slides

Materials:

bullet

Compound Light Microscope

bullet

Materials for making a "wet" mount slides of onion skin and squamous epithelial cells from your mouth.

bullet

2 blank slides

bullet

2 cover slips

bullet

iodine stain (for onion skin staining)

bullet

Methylene blue stain (for mouth epithelial cell staining)

bullet

Sterile swab

bullet

Onion skin (epithelial) tissue

bullet

Squamous epithelial cells

Procedures: (Your instructor will provide an overview, demonstration, and assistance for this procedure)

Squamous Epithelial Cells

  1. Prepare a slide of squamous epithelial cells from your mouth as instructed (demonstration by the instructor)

  2. View it on low and high power. Collect information as requested by your post-lab question sheet.

  3. Label the diagrams and fill in the chart on your post-lab question sheet.

Onion Skin Cells

  1. Prepare an onion skin slide as instructed (demonstration by the instructor)

  2. View it on low and high power. Collect information as requested by your post-lab question sheet.

  3. Label the diagrams and fill in the chart on your post-lab question sheet.

horizontal rule

Post-lab Activity and Data Analysis

Results and Analysis:

  1. Answer the Post-Lab Questions

horizontal rule

Post-Lab Questions (html version)         Post-Lab Questions (Word version)

horizontal rule