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Questions and Answers for Discussion

Basic Microscopy-
An Important Skill for Plant Pathologists
Melissa B. Riley, Department of Plant Pathology and Physiology, Clemson University

Answers to Questions:

Many of the questions associated with this laboratory exercise are very specific to the laboratory in which it is being conducted. Microscopes vary between laboratories and the specific magnifications available may vary.

Q.  What components are present on the compound microscope that are not present on the dissecting microscope based on the figures?
Components found on the compound microscope that are not found on the dissecting microscope include: condenser, condenser or iris diaphragm lever, condenser adjustment knob, fine focus, and objectives.

Q.  What components are present on the dissecting microscope that are not present on the compound microscope?
The dissecting microscope has a mirror, mirror axle, and a magnification knob. In some cases they may have an auxiliary or supplemental magnification lens.

Q.  Note the differences between your compound microscope and the compound microscope illustrated in Figure 1. If components are in different locations, these altered locations should be noted below.
This is specific to individual laboratories.

Q.  Is your dissecting microscope different from the one illustrated in Figure 2? If so, please note differences below for your dissecting microscope.
This is specific to individual laboratories.

Q.  What is the magnification of your eyepieces on your dissecting and compound microscope?
Dissecting usually 10x or 15x
Compound usually 10x or 15x

Q.  What are the magnifications of objectives of your compound microscope?
usually 4x, 10x, 45x
Does your microscope have an oil immersion lens?
specific to laboratory
What is its magnification?
if available usually 100x

Q.  What is the maximum magnification which you can obtain with your compound microscope? With use of oil?
specific to laboratory, 1000x in mine
Without use of oil?
specific to laboratory, 450x in mine

Q.  Does your dissecting microscope have an auxiliary or supplemental magnification lens at the bottom of the objective cover (Figure 3)?
specific to laboratory
If so what is its magnification factor?
specific to laboratory, in mine 1.5x

Q.  What is the minimum and maximum magnification that you can obtain when using the adjustment associated with your magnification knob located on the side of your dissecting microscope (Figure 4)?
Varies with laboratory, in mine 0.7 to 4.2x

Q.  What is the maximum magnification available when using your dissecting microscope? Remember to include the auxiliary or supplemental lens factor if present on your microscope and the maximum for the adjustable magnification knob and eyepieces.
specific to laboratory, in mine it is 94.5x

Compound Microscope

Q.  Draw what you observe. Note the top of the "e" as you look through the microscope. How does the position of the top of the "e" compare with what you observe when you are not looking through the microscope? Are they different?
the image is upside down from what you see without the microscope

Q.  If you want to look at the material on the left side of your image which way do you need to move the slide?
to the left

Q.  If you need to look at the material at the top of your image which way do you need to move the slide?
away from you

Q.  Why is this important?
So that you can determine which part of the sample you have been observing when you look at it without the microscope

Q.  Note the differences that you can see within the "e" when you switch to higher magnification below.
You begin to see that the "e" is not solid but is made up of pinpoints of ink - sometimes the "e" may actually have gaps

Dissecting Microscope

Q.  Draw the orientation of the "e" within a circle. Are there any differences from what you observed earlier with the compound microscope? If so, what are they?
the orientation is the same as if you were looking at the sample without the microscope

Q.  Determine the magnification of your sample using the following formula. You may need to estimate the magnification setting on the magnification knob. There is a line indicating the point at which to estimate the magnification associated with the magnification knob.
Eyepiece X Auxiliary Lens X Magnification Knob Setting = Total Magnification
15x (eyepiece) X 1.5x (lens) X 2.5x (magnification knob setting) = 56.25x

Q.  When you move materials to the left or away from you which way does the image that you observe through the microscope move? Is this different or the same as what you observed with the compound microscope?
If you move the sample to left image goes to the left, if you move the sample away from you the image moves away from you - yes it is different from the compound microscope

Q.  When would you want to use a light source that is shining directly on the sample (light positioned above the sample)? What is the advantage of this?
When the sample is not transparent or semi-transparent - for example when you are looking at spores or spore structures on the surface of leaf, stem, or fruit you need the light above the sample.