Limitless Exam · 2.2.4

Advanced Magnification: Avoiding Unit Traps

Paper 4 & Paper 6 Past Paper Style · 15 Questions · Cambridge IGCSE Biology 0610

Section A: Conversions (5 Qs)Section B: Unit Traps (5 Qs)Section C: Actual Size (5 Qs)

The Golden Triangle — Magnification Formula

Cover what you want to find

M = Image size (I) ÷ Actual size (A)A = I ÷ MI = M × A

Unit Ladder

mm → μm: × 1000μm → mm: ÷ 1000⚠ MATCH UNITS before dividing!

Q1 · Section A⇄ Unit Conversions

Convert 32 mm into micrometres (μm).

💡1 mm = 1000 μm

Q2 · Section A⇄ Unit Conversions

Convert 4.5 μm into mm.

💡Divide by 1000 to go from μm → mm

Q3 · Section A⇄ Unit Conversions

Convert 0.08 mm into μm.

💡1 mm = 1000 μm

Q4 · Section A⇄ Unit Conversions

Convert 250 μm into mm.

💡Divide by 1000 to convert μm → mm

Q5 · Section A⇄ Unit Conversions

A red blood cell is 8 μm in diameter. Express this in mm.

💡Divide by 1000

Q6 · Section B🔬 Unit Trap Calculations (Magnification)

A drawing of a chloroplast is 40 mm long. The actual chloroplast is 5 μm long. Calculate the magnification.

💡TRAP: Both values must be in the SAME unit before dividing. Convert 40 mm → μm first.

Q7 · Section B🔬 Unit Trap Calculations (Magnification)

A drawing of a mitochondrion is 60 mm long. The actual mitochondrion is 3 μm. Calculate the magnification.

💡Convert 60 mm → μm, then apply M = I ÷ A

Q8 · Section B🔬 Unit Trap Calculations (Magnification)

A student draws a cell nucleus 25 mm wide. The actual nucleus is 5 μm wide. What is the magnification?

💡M = Image ÷ Actual. Match units first!

Q9 · Section B🔬 Unit Trap Calculations (Magnification)

A diagram of a bacterium measures 90 mm. The actual bacterium is 2 μm. Calculate the magnification.

💡Convert mm → μm, then M = I ÷ A

Q10 · Section B🔬 Unit Trap Calculations (Magnification)

A drawing of a ribosome is 15 mm. The actual ribosome is 0.025 μm. Calculate the magnification.

💡Convert 15 mm → μm first, then divide by 0.025

Q11 · Section C📐 Extracting Actual Size

A micrograph has a magnification of ×2000. A cell on the micrograph measures 60 mm. Calculate the actual size of the cell in μm.

💡Rearrange M = I ÷ A → A = I ÷ M. Then convert mm → μm.

Q12 · Section C📐 Extracting Actual Size

A micrograph at ×500 magnification shows a cell measuring 45 mm. Calculate the actual length in μm.

💡A = I ÷ M, then convert mm → μm

Q13 · Section C📐 Extracting Actual Size

At ×10,000 magnification, a mitochondrion image is 30 mm long. What is the actual length in μm?

💡A = I ÷ M. Convert mm answer to μm.

Q14 · Section C📐 Extracting Actual Size

A micrograph (×4000) shows a chloroplast measuring 20 mm. Find the actual size in μm.

💡A = I ÷ M, then mm × 1000 → μm

Q15 · Section C📐 Extracting Actual Size

A scanning electron micrograph at ×50,000 shows a virus particle measuring 10 mm. Calculate the actual diameter in μm.

💡A = I ÷ M, convert result to μm

⚠ The 3 Rules of Magnification — Never Forget

Rule 1

Always convert drawing measurements from mm → μm before calculating magnification.

Rule 2

Formula: M = I ÷ A. Rearrange for actual size: A = I ÷ M.

Rule 3

Always state the unit in your final answer — μm or mm. No unit = no mark.

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