Microscope Measuring and Wet Mount Slides
Measuring with a microscope is pretty easy but you have to know the diameter of the FOV at each power. Remember, the diameter is the line from one side of a circle to the direct other side- it splits the circle into two equal halves. The diameter does not have to go across the middle; left to right! It can cut the circle at any two points as long as the two sides are equal- think of a pizza.
So, at low power the diameter is 4.5 mm, at medium power the diameter is 1.5 mm, and at high power the diameter is .45 mm. The FOV doesn't really shrink but the higher powers and closer lenses make the FOV appear to be smaller.
Now that you know the different diameters of the FOV, the rest is pretty easy. When you see something on the microscope you need to measure you simply ESTIMATE how MANY of that "thing" would fit across the diameter (see above). Then the math is: divide the FOV by the estimated number.
For example, I estimate that five things can fit across the diameter of the FOV at low power. That means the equation is 4.5mm / 5 = .9 mm. The same object at medium power might be estimated to fit 1.3 across the FOV. The equation for medium power would be 1.5mm / 1.3 = .88 (.9) mm. At high power the object would be too big to estimate a size for- but that doesn't matter as you already know the size and it doesn't change!
Ultimately, the math is always the same. The reason to know the FOV diameters is so that you can use different magnification powers. Some things might be too small to estimate (without a LOT of counting) at low power but at high power its simple OR maybe medium is the best view to estimate numbers.
Making a Wet Mount Slide
A wet mount slide is used for wet stuff! Duh! So, to make a wet mount slide you simply put a drop of "whatever liquid you are looking at" on the slide. Next, drag a cover slip from left to right at an angle so that the lower edge moves into the edge of the drop. The drop will collapse along that bottom edge. Once that happens, gently lay down the cover slip "like a door" to push our any air between the cover slip and the sample. You're done!