Q BankQuestion BankDocsDocuments

1.1.3—Magnification and actual size

Syllabus
9700–2028–2029
Objective
1.1.3
Level
AS

Magnification converts an object size into an image size

Magnification is the ratio of image size to actual size: it tells how many times larger the image is than the specimen.

M=IAsoI=M×AextandA=IMM=\frac{I}{A}\quad\text{so}\quad I=M\times A\quad ext{and}\quad A=\frac{I}{M}

  1. Identify the unknown quantity: magnification (M), image size (I) or actual size (A).
  2. Rearrange the relationship if needed.
  3. Convert image and actual sizes into the same unit before dividing or multiplying.
  4. Substitute, calculate, then report the size with its unit and a sensible precision.
  5. Sense-check: a magnified image should be larger than the actual specimen.

A 1 µm bacterium viewed at ×50 000 forms an image equivalent to 50 000 µm, or 50 mm. The unit conversion is part of the calculation, not an optional presentation step.

Magnification has no unit; image size and actual size do. Do not compare or combine lengths until their units match, and do not treat higher magnification as proof of higher resolution.

ConceptA-Level CAIE Biology AS