Microscopy Lab:

Care of the Microscope

The microscopes you will be using are compound light microscopes. They are sophisticated and expensive instruments and must be used with care. Mistreatment of microscopes may result in the need for costly repair work as well as your loss of user privileges.

To ensure the continued use of these microscopes, the following rules will be strictly adhered to.

Carry the microscope upright with two hands. The microscope must always be held upright. Place your dominant hand on the arm of the microscope with your other hand supporting the base of the microscope.

Inspect the microscope before use. All parts should move easily. If they do not, do not force them! Do not attempt any repairs! Report all damage, missing parts, or anything else to your teacher

Only clean the lenses with lens paper. The optical parts of the microscope are precision lenses and scratch easily. The only acceptable method of cleaning them is through the use of lens paper. DO NOT use paper towels, shirtsleeves, handkerchiefs, or Kleenex to clean lenses. Never remove oculars or other parts from the body tube of the microscope.

Do not push the microscope across the table. Sliding results in vibrations to the microscope that may result in the loosening of screws, or misalignment of parts.

Unplug carefully. Use care when plugging in and unplugging the microscope from electrical outlets.

Replace microscope properly. When finished with the microscope, turn off the light, remove the last slide from the stage, and wipe any water or other materials from the stage.. Neatly wrap your electrical cord around the neck of the microscope. If it had a bag, place the bag over the microscope and put it back in its cabinet.

Focusing the Microscope

Before starting, there are a few important ideas and details to keep in mind when focusing the microscope.

Always begin viewing every slide using the low power (4x) objective. Never begin an observation with the medium or high-powered objectives.

Estimating Size of Specimens under the Microscope

Purpose: To determine an approximate field of view diameter for each of the objective lenses on our microscopes in order to calculate the approximate size of a specimen.

Part 1: Wet-Mount Technique: Elodea Canadensis cell

  1. Place a drop of water on a clean slide.
  1. On your bench is a watch glass with a small plant specimen. Remove one single leaf. Smaller leaves will give a better result.
  1. Place the leaf in the drop of water on your slide and at an angle,carefully place the coverslip onto the drop of water and leaf.

If you have large air bubbles under the cover slip, start over and try again. It can take practice!

  1. Make sure your microscope has the low power (4x objective) in place. Place the slide on the microscope stage so that the drop of water on the slide is directly under the objective lens.
  1. Use the coarse adjustment knob to raise the slide until the cells come into focus under the ocular lens.

Since this is a plant, you will see a sheet of cells. Focus on just one cell for the rest of the lab.

  1. Use the fine adjustment knob to refine your focus. Don’t forget to adjust the diaphragm to get more light/contrast.
  1. Once the specimen is focused on low power, switch to medium (10x objective) power and refocus using both the coarse and fine adjustment knobs. Do the same thing on 20X and finally 40X.
  1. On unlined white paper, draw one elodea cell under medium (40x objective) power.

Remember to follow the lab drawing rules we just went over or refer to the last page in your unit packet.

  1. Estimate the approximate size of one elodea cell in mm. Show your working. Record this next to your drawing.

Refer to PART C of Microscope Math in your unit packet if you forgot how to do this.

  1. Now you will figure out the drawing magnification, or how many times larger your drawing of the Elodea is compared to life size. Add a labeled scale bar to your drawing and show all of your working.

Your answer should be labeled: ______X times larger than life

Refer to PART D of Microscope Math in your unit packet if you forgot how to do this.

Part 2: Prepared Slide: Various specimens

  1. Place the prepared slide under the microscope on low (4x objective) power.
  1. Focus on the specimen on low power using both the coarse and fine adjustment knobs.
  1. Once the specimen is focused on low power, switch to medium (10x objective) power and refocus using both the coarse and fine adjustment knobs.
  1. Once the specimen is focused on medium power, switch to high (40x objective) power and refocus using only the fine adjustment knob.
  1. On unlined white paper, draw a diagram of your specimen as seen on medium or high power, following the lab drawing rules.
  1. Next to your drawing, estimate the size of your specimen in µm- showing all your work.
  1. Now you will figure out the drawing magnification, or how many times larger your drawing of the specimen is compared to life size. Add a scale bar to your drawing and show all of your working.

Your answer should be labeled: ______X times larger than life

Refer to PART D of Microscope Math in your unit packet if you forgot how to do this.