Microscopes: parts, types and total magnification

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. Read this first

   Field of view (example data)

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

2. 1.

   At 100× Ari counts 128 evenly spread cells in the field. About how many cells will the 400× field show?

   • About 32 cells, since the field is 4 times narrower
   • About 2,048 cells, since 400× shows 16 times more
   • About 8 cells
   • About 512 cells, since 400× is 4 times more
3. 2.

   Use π ≈ 3.14. Esme estimates the cells on the whole cover slip. About how many are there?

   • About 3,600 cells, from 9 × 400
   • About 5,700 cells, using 0.45 as the radius
   • About 8,000 cells, from 9 ÷ 0.45 per mm
   • About 23,000 cells
4. 3.

   “Example data:” Kira sized a cell on a poster copy using the original photo's bar. Which result is right?

   • 216 µm, multiplying 36 by 6
   • 1.8 µm, halving the answer for the enlargement too
   • 7.2 µm, using the original 30 mm bar
   • 3.6 µm, using the poster copy's own 60 mm bar
5. 4.

   “Three ways a figure can show size (example data):” A figure will be resized for a poster. Luz wants a size reading that stays correct. Which feature should the figure carry?

   • The date on which the photo was taken
   • A scale bar drawn inside the picture, so it resizes with the picture
   • A magnification label such as 400×, printed under the picture by the camera
   • A note naming the objective lens used, such as 40×
6. 5.

   1 nm = 1,000 pm. A headline says a new light microscope at 20,000× shows single atoms, about 0.1 nm wide. Milo checks the table. Which reply is best?

   • Not possible: light microscopes cannot go above 400×, whatever lens is used
   • Possible: 20,000× is far more than the 400× in the table, so atoms would show
   • Not possible: light microscopes cannot separate points closer than about 200 nm
   • Possible: 0.1 is smaller than 200, so atoms are easy to separate with enough light
7. 6.

   Published width: about 8 µm. 1 mm = 1,000 µm. Noah finds the real width of red blood cells from the photo. Which statement is best supported?

   • The real width is about 1,296 µm, the mean photo width times the 400× power
   • The real width is 3.24 µm, the mean width as measured on the photo itself
   • The real width is about 0.0081 µm, since 3.24 ÷ 400 is 0.0081 and the unit is µm
   • The mean photo width is 3.24 mm, so the real width is about 8.1 µm, close to 8 µm

8. Counting yeast (example data)

   measure	value
   field diameter at 400× (mm)	0.45

9. 7.

   Pia wants the density of yeast cells (cells per mm²) on a slide. Which plan is best?

   • Count five fields, each at a different power, and then average the five counts together
   • Count the clearest field at 400× and report that count as the density of the whole slide, as is
   • Count five fields at 400×, find one field's area from 0.45 mm, and average the counts per mm²
   • Count one field at 400× and multiply that count by 400, the power used on the slide

10. Two electron microscopes (facts from OpenStax Biology 2e)

    kind	how the beam works	what it shows
    scanning	moves back and forth across the surface	surface details
    transmission	passes through a thin slice	internal structures

11. 8.

    A caption says a scanning electron micrograph shows the mitochondria inside a cell. Ren checks the card. Which reply is best?

    • Right: scanning means the beam scans through the whole cell from top to bottom
    • Doubtful: electron microscopes cannot show organelles in a cell, just whole cells in total, at most
    • Doubtful: scanning images show surface details; insides need a transmission image of a slice
    • Right: electron microscopes show the inside of any cell they are used on
12. 9.

    1 mm = 1,000,000 nm. Tala assumes the eye can separate points 0.2 mm apart on the image. A lens resolves 200 nm. About what total magnification is the most useful?

    • About 100,000×, the most an electron microscope reaches
    • About 40,000,000×, from 200,000 × 200
    • About 1,000×, since 200,000 nm ÷ 200 nm is 1,000
    • About 1×, since 0.2 and 200 are close
13. 10.

    1 mm = 1,000 µm. Zee reads a cell as 20 mm long, with a ruler good to ±1 mm. What range of real lengths is fair?

    • 39.9 to 40.1 µm
    • 38 to 42 mm
    • 9,500 to 10,500 µm
    • 38 to 42 µm