Introduction to the Light Microscrope

1. Examine your microscope. Familiarize yourself with the parts of the microscope. Recall the parts of it from your exercise in labeling the microscope.

The magnification written on the ocular lens (eyepiece) is ______

The low objective (this is the first and smallest number written on it) _____ x

The medium power objective is ______x

The high power objective is ______x

2. The total magnification using the lenses can be determined by multiplying the objective lens with the ocular lens. What is the total magnification of an item viewed with the:


3. Examine the diaphragm (underneath the stage). The numbers on the edge of it range from ONE to _____. Which number lets in the most light? __________ Which number lets in the least amount of light? ________

4. Look into the eyepiece, twist it left and right. Notice the line inside with an arrow on the end of it that moves as you twist. What do you think this is for? __________________________________________________________________________ Ask you teacher to explain what this is used for if you can't figure it out.

5. Place the slide of the "letter e" on the stage so that the letter is over the hole and is right side up. Use the low power objective to view the letter and use the coarse knob to focus. Repeat on the medium power objective. Finally, switch to high power. Remember at this point, you should only use the FINE adjustment knob.

Draw the "e" as it appears at each magnification. Drawings should be drawn to scale and you should note the orientation of the e in the viewing field (is it upside down or right side up?)

Have your parner push the slide to the left while you view it through the lens. Which direction does th E appear to move?__________________________________________________________________________________________


Letter "e" in low power
Letter "e" in medium power
Letter "e" in high power

6. Choose 2 specimens from the box of "common things". Use the circles below to sketch your specimens under LOW power. You may practice focusing with the high power, but you do not need to sketch it. Label your specimens from the name written on the slide.

Specimen 1 _______________________
Specimen 2 __________________

Draw in Low Power





Draw in Low Power







Obtain a slide with 3 different colored threads on it. View the slide right where all three threads cross each other under the medium or high power objective lens.

You should note that while you focus on one color of thread. The other threads become fuzzy. The microscope can only focus on one area at a time. Figure out which thread is on top by lowering your stage all the way (hint: Have your lab partner look from the side when you are moving the stage), then slowly raising it until the thread comes into focus. The first thread to come into focus is the one on top. Sketch the slide below using the low power objective lens. Identify the top, middle, and lower thread colors.


Which color thread is on top? _____________
Which color thread is in the middle? ______________
Which color thread is on the bottom? ____________

8. Answer true or false to each of the statements

__________ On high power, you should use the coarse adjustment knob.
___________If you move the slide to the left, the image when you are looling through the eyepeice appears to move right.
__________ The diaphragm determines how much light shines on the specimen.
__________ The low power objective has a greater magnification than the high power objective.
__________ The fine focus knob moves the stage up and down, but only in small increments.
__________ Images viewed in the microscope will appear upside down.
__________ If a slide is thick, only parts of the specimen may come into focus.
__________ The type of microscope you are using is a scanning electron microscope.
__________ For viewing, microscope slides should be placed on the objective.
__________ In order to switch from low to high power, you must rotate the revolving nosepiece.
__________ The total magnification of a microscope is determined by adding the ocular lens power to the objective lens power

This assignment was adapted from:, Ms Muskoph