A student prepared a slide of pollen grains from a flower. First the pollen was viewed through the low-power objective lens and then, without moving the slide, viewed through the highpower objective lens of a compound light microscope.

Which statement best describes the relative number and appearance of the pollen grains observed using these two objectives?

(1) low power: 25 small pollen grains

high power: 100 large pollen grains

(2) low power: 100 small pollen grains

high power: 25 large pollen grains

(3) low power: 25 large pollen grains

high power: 100 small pollen grains

(4) low power: 100 large pollen grains

high power: 25 small pollen grains

(2) low power: 100 small pollen grains

high power: 25 large pollen grains

Explanation:

Compound light microscopes are devices used to greatly magnify objects. They have several objective lenses, a low-power lens magnifies 10 times (10X) the objects, and the high-power lens magnifies them 40 times (40X).

For that reason, when observing the pollen grains with the high-power lens the student will see them bigger than with the low-power lens. However, the field of view (the visible area through a lens) is reduced when a higher power lens is used, so fewer pollen grains will be seen.

The answer therefore is the option of higher number of pollen grains of small size for the low-power lens, and lower number of pollen grains of larger size for the high-power lens.