Passage III

A student performed 3 activities with a microscope that had 4 objective lenses.

Activity 1

The student viewed 4 slides (A, B, C, and D) through each objective lens. Each slide had 2 thin lines painted on it. For each objective lens, the student determined whether she could see the lines as separate or whether they blurred into 1 image. The results appear in Table 1.

Activity 2

The student was given a prepared slide with a line on it that was 0.1 mm in length. This length was defined as the object size. Next, she viewed the slide with each objective lens, estimating how long the line appeared. This estimated length was called the image size. Finally, she calculated the magnification (M) associated with each objective lens from the following formula:

M = image size ÷ object size.

The data appear in Table 2.

Activity 3

The numerical aperture (NA) of each objective lens was printed on the microscope. NA determines how much detail can be seen and is related to resolution (R). R is defined as the smallest distance separating 2 objects such that the objects appear separate. Thus an objective lens with a small R shows a sample more clearly than does an objective lens with a large R. R is calculated from the fol-lowing formula:

where is the wavelength of the light, in nanometers (nm), used to view the objects.

The student calculated R for each objective lens, assuming a of 550 nm. The data appear in Table 3.