Using a Light Microscope

Using a Light Microscope

In a previous lesson, you learned the parts of a compound light microscope. In today's lesson, you will use a microscope to view specimens. Before you begin, review the parts of the microscope by completing the game.

Using a Light microscope notes

Open Science Notebook to Using a Light Microscope Notes. Use this page as a guide to help you record the most important details of the lesson.

Using a light microscope

In today's lesson, you will use materials from the microscope box found in your curriculum kit. You will also need individual items from your curriculum kit. Gather the following materials so that you will have them ready for the activities in today's lesson:

Pencil
Microscope
Frog blood smear slide
Onion bulb epidermis slide
Wool fiber slide

Remember to install the eyepeice!!

​How to use a microscope

Today, you will use the compound light microscope to view specimens. You will use all three objectives to view each specimen. The revolving nosepiece is the part of the microscope that you turn to change objectives.

​Recall that each objective contains a lens that magnifies the specimen in addition to the lens in the eyepiece. To find the total magnification, or number of times larger a specimen appears than its actual size, multiply the value of the eyepiece by the value of the objective.

Multiple Choice

Juan Carlos viewed a pine needle using his light microscope. He used medium power, which had the notation 20X on the side. What was the total magnification of the specimen?

• 20X

• 30X

• 100X

• 200X

How to use a microscope

​Always begin with the lowest objective lens!

Start with 4x objective,

Then 10x objective,

Then 40X objective.

Obtain your Wool Fibers Slide

​Follow the procedures below:

1. Press the end of the switch with a single line to turn on the light source.

2. Slide the stage clips outward. Hold the slide by the edges to avoid making fingerprints. Place the slide on the stage. Use the stage clips to secure the slide in place.

3. Turn the revolving nosepiece so the 4X objective is above the slide.

4. Look through the eyepiece using one eye. If you wear glasses, you may wish to remove them while using the microscope.

5. Turn the focus knob to bring the image into focus. Do not allow the slide to press against the objective.

6. Slowly move the slide to center the specimen in the field of view. Remember that small movements can shift your magnified image more than you expect.

7. Spin the revolving nosepiece to the 10X objective. Use the focus knob to refocus the image. Repeat with the 40X objective.

8. Rotate the diaphragm to adjust the amount of light that passes through the specimen.

• Robert Hooke

" By the help of microscopes, there is nothing so small, as to escape our inquiry; hence there is a new visible world discovered to the understanding. " 

Onion Bulb Epidermis

Now, you will view the onion bulb epidermis using the microscope. The onion's outermost layer is also called the epidermis. You also have an epidermis, but you usually call it your skin. The specimen on the onion bulb epidermis slide is a piece of the outermost layer of an onion like the ones shown here.

You likely noticed that the onion specimen you saw through the microscope had lines and dots in shades of blue and pink. An actual onion epidermis is clear, so you would not normally see the details of the specimen. Scientists often add stain, which is a dye that makes some structures in the specimen stand out. The pink and blue shades you observed are caused by the stain.

Multiple Select

Which of the following statements are true about what you see when viewing the onion bulb epidermis through the microscope?

• 
  The roots, bulb, and leaves are all visible through the microscope.

• 
  The microscope shows dots and outlines that are not visible in the actual onion.

• 
  The microscope shows several onions all at once instead of a single onion.

• 
  The specimen under the microscope looks like a different color than the actual onion.

Frog Blood

Did you know that blood contains cells? Blood is actually a mixture of fluid called plasma and blood cells. Now, you will view frog blood cells using the compound light microscope. Frog blood cells look very similar to human blood cells.

​There are two major types of blood cells that you can view on the frog blood smear slide:

• white blood cells

• red blood cells

As you examine the slide under the microscope, try to find both red and white blood cells.

​When you focus the slide using high power, pay attention to the way the different cells come into focus as you move the stage up and down.

Multiple Choice

Which of the following best describes the focus of the microscope on blood cells using the high-power objective?

• None of the cells are ever in focus.

• All of the cells are in focus at the same time.

• Only some cells come into focus at any one time.

Stereo microscope mode

Now, you will view a specimen using stereo microscope mode.
To change to the stereo microscope, simply change to the upper light source. Press the side of the switch with two lines to turn on the upper light source.

Instead of using a slide, place a solid object on the stage to view using stereo microscope mode.

Viewing pencil tip in stereo mode

Follow these steps to view your pencil in stereo microscope mode. As you do so, compare the location of the stage when the pencil is focused to its location when focusing a slide.

1. Press the side of the switch with two lines to turn on the overhead illumination.

2. Rotate the revolving nosepiece to the 4X objective.

3. Place the pencil on the stage so that the tip of the pencil is over the hole in the stage.

4. Turn the focus knob to raise and lower the stage to focus on the pencil.

5. Rotate the revolving nosepiece to examine the pencil using the 10X objective.

Do not use the 40X objective in stereo microscope mode. Trying to use the high-power objective in stereo microscope mode may damage the device.

Multiple Choice

True or false:

The stage needed to be lower to focus on the pencil than to focus on a slide.

• True

• False

​Have a shocking day!!!