Lab 3: Light Microscopy
What is the magnifying power of the ocular lenses on your microscope?
The magnifying power of the ocular lens is marked on the lens barrel (usually 10x).
What type of object do you study with a stereomicroscope?
Whole, opaque.
The resolving power of a light microscope is lower than that of an
electron microscope.
To locate small objects on a slide, first find them under; then place them in the center of the field before rotating to;
low power high power
Which part of the microscope controls the amount of light?
Diaphragm.
What adjustment knob is used with high power?
Fine adjustment knob.
What is the final item placed on a wet mount before viewing with a light microscope?
Coverslip.
If the thread layers are red, brown, green, from top to bottom, which layer will come into focus first if you are using the microscope properly?
Green.
Does low power or high power have a smaller field but magnifies to a greater extent?
High power.
Of the three microscopes studied, which one best shows the surface of an object?
Scanning electron microscope.
If Euglena are swimming to the left, which way should you move your slide to keep them in view?
Right.
Estimate the number of millimeters, to tenths, that you see along the field. Convert the number to micrometers.
Approximately 1.6mm Approximately 1,600/um.
What word is used to indicate that if the object is in focus at low power it will also be in focus at high power?
Parfocal.
Which way does the image appear to move?
Opposite. When moved to the right, the object appears to move to the left.
Identify the following parts on a microscope, and label them.
(left, top to bottom): eyepiece(s) (ocular lens or lenses); body tube; nosepiece; objective lens or lenses; stage or mechanical stage (optional); diaphragm/diaphragm control lever; condenser. (right, top to bottom): arm; stage clips; coarse-adjustment knob; fine-adjustment knob; light source; base.
lpd = low-power diameter of field (in micrometers) lpm = low-power total magnification hpm = high-power total magnification
1,600/um 100x 400x
Use the micrometer row to convert 1/um to millimeters. hint: (1mm=1000/um)
1/um = 0.001 mm
Low power Ocular Lens Objective Lens Total Magnification
10x 10x 100x
High power Ocular Lens Objective Lens Total Magnification
10x 40x 400x
Scanning power (if present) Ocular Lens Objective Lens Total Magnification
10x 4x 40x
Use the meter row to convert 1m to /um
1m = 1000mm = 1,000,000/um
Which type of microscope would you use to view a Euglena swimming in pond water?
Compound light microscope.
Does low power or high power have a larger field of view? (allowing you to see more of the object)
Low power.
A total magnification of 100x requires the use of the 10x ocular lens with which of the objective lenses?
Lower power objective.
Which objective always should be in place both when beginning to use the microscope and also when putting it away?
Lower power objective.
What unit of metric measurement is most useful for light microscopy?
Micrometer.
What are the ocular lenses?
The lenses located near the eye.
What differences do you notice?
The letter is inverted - that is, it appears to be upside down and backward compared to its appearance when viewed by the unaided eye.
Draw the letter e as it appears on the slide (with the unaided eye, not looking through the eyepiece).
The letter should be in the normal position e.
Draw the letter e as it appears when you look through the eyepiece.
The letter should be upside down and reversed.
What does compound refer to in the designation compound light microscope?
This type of microscope uses two sets of lenses and light to view an object.
What is the magnifying power of the low-power objective lens on your microscope?
Usually 10x.
What is the magnifying power of the high-power objective lens on your microscope?
Usually 40x.
What is the magnifying power of the scanning lens on your microscope?
Usually 4x.
