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Biology · Grades 7–10

Microscope scales and magnification

Distinguish a bigger image from a more detailed image.

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Learn the idea

Magnification

Magnification = image size / actual size, with matching units.

Resolution

Resolution is the ability to distinguish nearby details; enlarging a blur does not necessarily improve it.

Scale bar

A scale bar provides a size reference in the image and remains useful when image and bar scale together.

Units

1 mm = 1000 µm. Convert units before calculating a size ratio.

Worked examples

An object is 20 µm long and its image is 2000 µm long. Find magnification.

2000/20 = 100 times.

100

Convert 0.4 mm to micrometers.

0.4 × 1000 = 400 µm.

400 µm

Check your understanding

  1. Which term means distinguishing two nearby points?

    1. Only magnification.
    2. Specimen color.
    3. Resolution.

  2. At 200× magnification, an image is 10 mm long. Find the actual length in millimeters.

  3. Why can digitally enlarging an image fail to show new cellular detail?

Answers and marking notes

Answers and marking notes
  1. Resolution.

    Resolution concerns detail separation.

  2. 0.05 mm

    10/200 = 0.05 mm.

  3. It may enlarge existing pixels without improving the captured resolution.

    Bigger does not necessarily mean more information.

Further reading and review references

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Independent educational review required. Grade bands are approximate; these are not officially aligned curricula.