Question

example #2: ocular power = 10x power objective = 10x high power objective = 40x the diagram shows the edge of a millimeter ruler viewed under the microscope with the lenses listed above. the field shown is the low power field of view. a) what is the approximate width of the field of view in micrometers? b) what would be the width of the field of view under high power? c) if 5 cells fit across the high power field of view, what is the approximate size of each cell?

Explanation:

Step1: Determine low - power magnification

The low - power magnification is the product of the ocular power and the low - power objective power. Given ocular power = 10x and low - power objective = 10x, so the low - power magnification $M_{low}=10\times10 = 100$x.

Step2: Estimate low - power field of view

Assume that the field of view of a 100x magnification is about 1000 micrometers (a common estimate for a light microscope at 100x magnification). So the width of the low - power field of view $d_{low}=1000$ micrometers.

Step3: Determine high - power magnification

The high - power magnification is the product of the ocular power and the high - power objective power. Given ocular power = 10x and high - power objective = 40x, so the high - power magnification $M_{high}=10\times40 = 400$x.

Step4: Calculate high - power field of view

The relationship between the field of view and magnification is inversely proportional. Let $d_{low}$ be the low - power field of view and $d_{high}$ be the high - power field of view. Then $\frac{d_{low}}{d_{high}}=\frac{M_{high}}{M_{low}}$. Substituting the values, we get $d_{high}=\frac{M_{low}}{M_{high}}\times d_{low}=\frac{100}{400}\times1000 = 250$ micrometers.

Step5: Calculate cell size

If 5 cells fit across the high - power field of view, and the high - power field of view is 250 micrometers, then the size of each cell $s=\frac{250}{5}=50$ micrometers.

Answer:

a) 1000 micrometers
b) 250 micrometers
c) 50 micrometers