Introduction to the Light Microscope

Students learn to use a basic light microscope by examining the structures and using a prepared slide of the letter “e” to practice focusing.  Activity includes step by step instructions on how to focus a slide on high power, something  beginner biologists often have difficulty with. 

The instructions were made for basic light microscopes that have three objectives: scanning, low, and high power (400x), though it could be modified to work with other microscopes.

Basic Instructions for Using the Light Microscope

  1. Prepare the Workspace: Ensure you have a clean, well-lit, and stable surface for setting up the microscope. Keep the area organized and free from clutter.
  2. Turn On the Light Source: If your microscope has an adjustable light source, switch it on. Adjust the brightness to an optimal level for viewing the specimen.
  3. Place the Slide: Place the prepared slide on the stage of the microscope. Secure it in place using the mechanical stage clips or slide holder.
  4. Use the Lowest Objective Lens: Start with the lowest magnification objective lens (usually 4x or 10x) by rotating the nosepiece to position it over the slide.
  5. Adjust the Focus: Look through the eyepiece and slowly turn the coarse focus knob to bring the specimen into a rough focus. Then, use the fine focus knob for precise focusing. Continue adjusting until the image is clear.
  6. Change to Higher Magnification: If needed, switch to higher magnification lenses (40x or 100x) by rotating the nosepiece. Be cautious with higher magnifications as they have a smaller depth of field and require more precise adjustments.
  7. Center the Specimen: Adjust the mechanical stage controls to move the slide and center the area of interest within the field of view.

Students are also allowed to explore the microscope by looking at slides of common things and making sketches.  The worksheet includes basic questions about microscope use and an essay question about how to help another student focus using the high power objective.

Grade Level:  7-10 |  Time Required:  40-50 minutes