Mini Lab: Operating the Microscope
Purpose:
You will use the microscope to examine tiny specimens.
Procedure:
Part A: Practice Using the Microscope
1. Obtain a microscope from the cupboard. Remember to carry the microscope with two hands.
2. Place the letter e right side up on the microscope stage.
3. In order for the letter e to be the right side up, how must you orient your slide on the stage?
A: upside
down
4. Focus at the e under low power. Bring the image into focus using the coarse adjustment first and
then the fine adjustment knob second. Draw what you see under the microscope.
5. Change to medium power. Bring the letter e into focus using the coarse adjustment first and then
the fine adjustment knob second. Draw what you see under the microscope.
6.
Change to high power. Be careful. Make sure the high power objective lens does not touch the
slide. Bring the letter e into focus using only the fine adjustment knob on this power. Draw what
you see under the microscope.
LOW POWER e
MEDIUM POWER e
HIGH POWER e
Part B: Movement of the Image
1. Switch back to low power.
2. On low power, move the letter e to the left, and then to the right.
movement of the image.
Record the resulting
3. On low power, move the letter e away from you and towards you.
movement of the image.
Movement of the Slide
to the left
to the right
away from you
towards you
Record the resulting
Resulting Movement of the Image
right
left
towards
away
4. If the letter e is in the top left hand corner of the field of view, what direction must you move
the slide to bring it to the center?
A: to
the left and away from you
5. Put the slide of the letter e back into proper tray.
Part C: Measuring the Field of View (Field Diameter)
1. The field of view (field diameter) is the circle of light seen through the microscope.
2. Using a transparent ruler, measure the field of view (field diameter) on low, medium and high
power. Record your answer in the below.
low field diameter: 4.5 mm
medium field diameter: 1.8
mm
high field diameter: 0.45
mm
3. What happens to the field of view (field diameter) when you switch from low power to medium
power?
A:
you focus on a smaller area of space in greater magnification
Part D: Examining Depth of View
1. Observe a prepared slide of silk fibers. DO NOT use high power. You may break the slide or
the lens.
2. Why can’t you focus on all of the silk fibers at the same time at medium power?
A: microscope
can only focus on one depth at a time
Part E: Determining the Size of a Specimen
1. Obtain a slide of a fruit fly. Observe the fruit fly at LOW power only. You may damage the slide or
microscope if you use the medium or high power objective lens.
2. Draw the fruit fly on low power.
3. Provide an estimate of how many fruit flies would fit across your field of view when looking at your
specimen.
A: 1
fruit fly when looking
through microscope
70 mm
drawing length
4. Estimate the size of the fruit fly.
estimated size of specimen: 4.5 mm/fly
magnification of drawing: 15X
estimated size of specimen = field diameter
fit number
The fit number refers to the number of times a specimen fits across the field diameter (field of view).
estimated size of specimen = 4.5 mm = 4.5 mm/fly
1 fly
Part F: Calculating Magnification of Drawing
1. Use a ruler measure the size of your fruit fly and express your answer in mm.
Magnification of Drawing = measured size of drawing (mm)
estimated size of specimen (mm)
Magnification of Drawing = 70 mm = 15X
4.5 mm
1cm = 10 mm
1 mm = 1000 um (micrometers)
Part G: Microscope Math
Power
Ocular Lens
Magnification
Objective Lens
Magnification
Total
Magnification
My
Measured
Field
Diameter
The Actual
Field Diameter
low
10X
4X
40X
4.5 mm
medium
10X
10X
100X
1.8 mm
high
10X
40X
400X
0.45 mm
1. Calculating Medium Field Diameter:
Medium Field Diameter (MFD) =
Low Field Diameter
(LFD)
Low Magnification
(LM)
Medium Magnification (MM)
2. Calculating High Field Diameter:
High Field Diameter (HFD) =
Low Field Diameter (LFD)
Low Magnification
(LM)
High Magnification (MM)