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?

   • 10 µm
   • 108 µm
   • 3.6 mm
   • 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: the cell on photo B is longer, 30 mm against 12 mm
   • No: cell A is 12,000 µm and cell B is 75,000 µm, so B is longer
   • No: photo A shows the larger cell, since its magnification is lower
   • Yes: both are 12 µm long
4. 3.

   1 mm = 1,000 µm. Esme measures two cells on photos at different magnifications. Which real cell is longer, and by how much?

   • The second, since 1,500 × 45 is bigger than 600 × 24
   • The first, by 21 µm, the gap between 45 and 24
   • The first, by 10 µm: 40 µm against 30 µm
   • The second, since its photo shows 45 mm against 24 mm

5. Field of view (example data)

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

6. 4.

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

   • 64 times smaller
   • 8 times smaller
   • 4 times smaller, like the diameter
   • 16 times smaller
7. 5.

   Kira treats the 400× field as a circle. Using π ≈ 3.14, about how large is its area?

   • About 0.16 mm²
   • About 0.64 mm², using 0.45 as the radius
   • About 1.4 mm², from 3.14 × 0.45
   • About 0.20 mm², from 0.45 × 0.45
8. 6.

   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?

   • 40,500 cells
   • 5 cells
   • 50 cells
   • 20 cells, the count at 100×
9. 7.

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

   • 60 mm
   • 60,000 mm
   • 6 mm
   • 0.027 mm
10. 8.

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

    • 125 µm
    • 500 µm
    • 125 mm
    • 200,000 µm
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?

    • 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
    • It shows the smallest bacteria clearly if the power is raised to 1,000×
    • It shows bacteria when they are alive, and not when they are preserved

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