Microscope

Microscope Lab Goals

  • Review metric system measurements.

  • Properly use and care for a scientific microscope.

  • Learn techniques for preparing cells for microscopy.

  • Understand the size of cells compared to visible objects.

  • Survey microscopic organisms from different kingdoms of life.

Objectives

By the end of this lab, you should be able to:

  • Identify parts of a microscope and their functions.

  • Properly carry, use, and store a microscope.

  • Prepare a wet mount slide.

  • View and focus specimens under a microscope.

  • Compare sizes of different cell types.

  • Estimate a cell's size using the field of view.

A. Metric System Review

  • The metric system is globally used for quantifying temperature, length, weight, and volume:

    • Temperature: degrees Celsius (°C)

    • Length: meters (m)

    • Weight: grams (g)

    • Volume: liters (L)

  • The metric system uses decimals, where smaller units use prefixes:

    • Centi- (hundredth, 0.01)

    • Milli- (thousandth, 0.001)

    • Micro- (millionth, 0.000001)

    • Kilo- (thousand, 1000)

  • Conversion example:

    • 1 meter = 100 centimeters (cm)

    • 200 m = 200 x 100 = 20,000 cm.

B. Compound Light Microscope

  • A compound light microscope is essential for studying biological samples not visible to the naked eye.

    • It illuminates specimens using bright light, producing inverted images at high magnification.

  • Lenses involved:

    • Objective lens: Magnifies the sample, located on the nosepiece.

    • Ocular (eyepiece) lens: Further magnifies the image.

  • To find total magnification: Objective magnification × Ocular magnification.

Important Usage Tips

  • Clean lenses with lens paper only.

  • Follow proper handling protocols:

    • Always start and end with low power.

    • Avoid wetting any part of the microscope.

    • Carry with one hand on the arm and one under the base.

  • Clean the microscope only with lens paper in the following order:

    • Lower surface of all objective lenses.

    • Ocular lens.

    • Condenser lens and light housing.

Microscope Parts

  • Eyepiece (Ocular lens)

  • Nosepiece ring (turret)

  • Objective lenses (low, medium, high power)

  • Stage

  • Stage controls

  • Iris diaphragm

  • Condenser lens

  • Light source

  • Coarse focus adjustment knob

  • Fine focus adjustment knob

C. Observing Specimens

  • Always begin with the low power objective lens and high nosepiece position before adding a slide.

  • Ensure the specimen is centered over the light source.

  • Focus using:

    1. Low power first.

    2. Then medium and high power, adjusting only with the fine focus knob.

Procedure for Viewing the Letter "E"

  1. Obtain the slide with the letter "e".

  2. Follow proper focusing procedure:

  • Focus, observe, and draw under each magnification.

  1. Record total magnification on the data sheet.

Working Efficiently in the Lab

  • Work collaboratively, preparing distinct specimen slides.

  • Observe and draw cells from each slide, ensuring original drawings for grading compliance.

Required Drawings

  • Detailing three cells from each specimen.

  • Label: specimen name, total magnification, and identifiable structures.

Dry Prepared Specimens

  • Examples:

    • Spirogyra: cell wall, nucleus, chloroplasts.

    • Paramecium: cytoplasm, vacuoles, nucleus.

    • Human Blood: white & red blood cells.

Wet Mounts Preparation Steps

  1. Use a flat slide and avoid depressions.

  2. Place a drop of medium on the slide before adding the specimen.

  3. Gently place a coverslip to minimize air bubbles.

Notice:

  • Handle specimens carefully and practice caution with staining materials as they can potentially stain skin and clothes.

Lab Check-out Protocol

  1. Ensure low power objective is in position.

  2. Raise nosepiece to top position.

  3. Remove slides and turn off light.

  4. Properly store the microscope.

Study Questions

  1. Identify microscope parts.

  2. Describe proper carrying methods.

  3. Explain how to correctly put away a microscope.

  4. Clarify magnification for high, medium, low power, and ocular lens.

  5. How is total magnification determined?

  6. Discuss the relationship between increased magnification and field of view.

  7. Importance of placing medium on a slide before the specimen.

  8. Method for locating a specimen when changing magnification.

  9. Differences between plant and animal cells.