Microscopes: parts, types and total magnification
Grade 9 Science Worksheet - Challenge Me
Circle the best answer.
Read this first
Two slides (example data)
slide magnification field diameter (mm) cells counted 1 100× 1.8 40 2 400× 0.45 6 Bo counts cells on two slides. Which slide has more cells per mm², and by how much?
- Slide 1, about 1.7 times denser
- Slide 2, about 2.4 times denser
- Slide 1, since it shows 40 cells against 6
- Slide 2, about 4 times denser
Use π ≈ 3.14. Esme estimates the cells on the whole cover slip. About how many are there?
- About 5,700 cells, using 0.45 as the radius
- About 23,000 cells
- About 3,600 cells, from 9 × 400
- About 8,000 cells, from 9 ÷ 0.45 per mm
Photo magnification 500×. The cell measures 8 mm on the photo. Note: 8 mm × 500 = 4,000 mm. Jun checks a classmate's note. Which fix is right?
- Keep the multiplying, but convert: 4,000 mm is 4 m long
- Ignore the magnification: the cell is 8 mm long
- Divide, but keep the unit: the cell is 16 mm
- Divide, not multiply: 8 mm ÷ 500 = 0.016 mm = 16 µm
“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
“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?
- A scale bar drawn inside the picture, so it resizes with the picture
- A note naming the objective lens used, such as 40×
- The date on which the photo was taken
- A magnification label such as 400×, printed under the picture by the camera
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 mean photo width is 3.24 mm, so the real width is about 8.1 µm, close to 8 µm
- The real width is about 0.0081 µm, since 3.24 ÷ 400 is 0.0081 and the unit is µm
- 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
Counting yeast (example data)
measure value field diameter at 400× (mm) 0.45 Pia wants the density of yeast cells (cells per mm²) on a slide. Which plan is best?
- Count the clearest field at 400× and report that count as the density of the whole slide, as is
- Count one field at 400× and multiply that count by 400, the power used on the slide
- Count five fields, each at a different power, and then average the five counts together
- Count five fields at 400×, find one field's area from 0.45 mm, and average the counts per mm²
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 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
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×, since 0.2 and 200 are close
- About 1,000×, since 200,000 nm ÷ 200 nm is 1,000
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?
- 9,500 to 10,500 µm
- 39.9 to 40.1 µm
- 38 to 42 mm
- 38 to 42 µm