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Anatomy
Anatomy
Tube that holds eyepiece.
Holds objective lenses and sometimes called a revolving turret. You choose lens by rotate to lens you want to use.
Most compound microscope come with 3/4 objective lenese revolving on nosepiece.
Supports holding slides in place on stage.
Where specimen is placed to observe.
6. Controls how much light pass slide. Located below stage and usually controlled by round dial. To set diaphragm = determined by magnification.
7. Build under the stage to send light through stage when observing.
8. Magnifies image of specimen. Also called ocular.
9. Connect base to nosepiece and also the part used to carry the object.
10. Move stage, providing general focus on specimen, main focus used.
11. Same as ☝Coarse focus but used as second focus.
12. Main support of object at the bottom.
Measurements Used
Measurements Used
Cell Size and Scale - Learn.Genetics
Cells are measured in micrometers or microns(μm).
Some are only half a micron in diameter, meaning that a meter length can fit two million cells.
1000 millimeters (mm) = 1 centimeter
1000 micrometers (μm) = 1 millimeter
1 000 000 nanometers (nm) = 1 micrometer
picometers () = 1 nanometer
angstrom () = 1 picometer
Magnification
Magnification
Microscope lenses are all convex lenses, the same type of lens in the eyes.
Total magnification = eye piece x objective lens
Microscope eyepieces all have a 10x lens.
Reminder: 1 mm = 1,000 μm
Lens powers | Objective Magnification x Total Magnification → Total Magnification | Field of Diameter
Low power | 4 x 10 →40 | 4.5 (mm)/4500 (μm)
Medium power | 10 x 10 →100 | 1.8 (mm)/1800 (μm)
High power | 40 x 10 → 400 | 0.45 (mm)/450 (μm)
1 - Coarse adjustment (big one) used first
2 - Fine adjustment (small one) used after
Calculation
Calculation
Finding the Field of View
Finding the Field of View
Abbreviated as FOV, it's the area observed when looking through a microscope. It essentially the same as the Field Diameter (FD), the diameter of the field of view.
Again, the scales are:
4x = 4.5 mm
10x = 1.8 mm
40x = 0.45 mm
Find the ratio of the magnification of the high-power objective lens to the lower one.
Objective Magnification high power lens (X)
ratio = ----------------------------------------------
Objective Magnification less power lens (X)
Then use the ratio to find the field's diameter by using the high power magnification to divide it
FOV low power (μm)
High power FOV = -------------------------
ratio
Finding the Size of Specimen and Magnification
Finding the Size of Specimen and Magnification
Both are often switchable.
high-power lens magnification
Ratio of High-Power lens Field of View = _____________________________
low-power lens magnification
lower-power magnification
Medium power field diameter (in μm) = ___________________________ X - power field diameter (μm)
medium-power magnification
low-power magnification
High power field diameter (in μm) = ___________________________ X - power field
high-power magnification
Finding the Size of Specimens
Finding the Size of Specimens
Chose the magnification with a clear image
Note the FOV/FD of the magnification
Estimate how many times the specimen could fit the field
Estimate the specimen's size with the formula:
width of the field of view (micrometer)
Estimated size of specimen = _______________________________________
fit number (amount of specimens that could fit across the area)
Drawing Magnification
Drawing Magnification
A biological drawing magnification tells how the size of the illustration compares with the actual size of the object.
Measured size of drawing (wide/length) in mm
Drawing Magnification = _____________________________________________
Estimated size of specimen (wide/length) in mm
Example 1: A student observed an amoeba under the 40x objective lens and noted that it took up 1/4 of the view. Find the actual size of the cell, in μm.
The amoeba is around 112.5 μm long.
First, find the ratio of high and low-objective lens magnifications:
40 (high power objective magnification)
ratio = ---------------------------------- = 10 (ratio used FOV)
4 (low power objective magnification)
Then, find the FOV:
FOV = 4500/10 = 450μm
Finally, use divide the FOV by the number of specimens that could fit in the field (which is 4, as it took 1/4 of the field):
450/4 = 112.5 μm
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