Microscopes: parts, types and total magnification

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   Bacterium on a photo (example data)

   item	length on the photo (mm)	real length (µm)
   scale bar	30	6
   bacterium	18	?

2. 1.

   Ari measures a bacterium on a photo. How long is the real bacterium?

   • 108 µm
   • 3.6 mm
   • 10 µm
   • 3.6 µm
3. 2.

   1 mm = 1,000 µm. Bo measures one kind of cell on two photos. Are the real cells the same length?

   • No: cell A is 12,000 µm and cell B is 75,000 µm, so B is longer
   • Yes: both are 12 µm long
   • No: the cell on photo B is longer, 30 mm against 12 mm
   • No: photo A shows the larger cell, since its magnification is lower

4. Field of view (example data)

   total magnification	field diameter (mm)
   100×	1.8
   400×	0.45

5. 3.

   Jun goes from 100× to 400×. The field is a circle. By what factor does the area of the field shrink?

   • 16 times smaller
   • 8 times smaller
   • 64 times smaller
   • 4 times smaller, like the diameter
6. 4.

   At 400× Luz counts 12 evenly spread cells in the 0.45 mm field. Using π ≈ 3.14, about how many cells are there per mm²?

   • About 19 cells per mm², using 0.45 as the radius
   • About 27 cells per mm², from 12 ÷ 0.45
   • About 12 cells per mm², the count itself
   • About 75 cells per mm²
7. 5.

   1 mm = 1,000 µm. Plant cells 90 µm long line up end to end across the 400× field. How many fit across, Milo asks?

   • 5 cells
   • 50 cells
   • 20 cells, the count at 100×
   • 40,500 cells
8. 6.

   A cell is 40 µm long. Noah photographs it at 1,500×. How long does the cell appear on the photo?

   • 60 mm
   • 6 mm
   • 60,000 mm
   • 0.027 mm
9. 7.

   1 mm = 1,000 µm. Pia reads the field number card. A cell spans one quarter of the field. How long is the cell?

   • 200,000 µm
   • 125 µm
   • 125 mm
   • 500 µm
10. 8.

    1 nm = 1,000 pm. Two points 150 nm apart blur together at 1,000×. Ren swaps in an eyepiece that doubles the total to 2,000×. What is seen?

    • Two separate points once the image is big enough to see
    • Two separate points, since 2,000× is twice as much
    • A bigger blur: 150 nm is still under the 200 nm limit
    • Nothing, because the image disappears at 2,000×
11. 9.

    1 µm = 1,000 nm. Tala reads that bacteria are about 0.1 to 5.0 µm wide. Which statement fits a light microscope?

    • It shows bacteria when they are alive, and not when they are preserved
    • It shows the smallest bacteria clearly if the power is raised to 1,000×
    • An electron microscope is required to show any bacteria, large or small
    • It cannot show the smallest bacteria clearly, since 100 nm is below the limit

12. Three jobs (example data)

    job	what must be seen
    A	a living amoeba swimming
    B	the 3-D surface of a pollen grain
    C	the inside of a mitochondrion

13. 10.

    Zee matches each job to a microscope. Which pairing is right?

    • A: light; B: transmission electron; C: scanning electron
    • A: scanning electron; B: light; C: transmission electron
    • A: light; B: light; C: transmission electron
    • A: light; B: scanning electron; C: transmission electron