Magnification Cambridge IGCSE Biology revision
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In plain words
Cells are far too small to see, so we look at enlarged pictures of them. Magnification is simply how many times bigger the picture is than the real thing. If you know any two of image size, real size and magnification, you can work out the third.
Three things to know
- Magnification = image size ÷ actual size.
- Rearranged: actual size = image size ÷ magnification.
- Both sizes must be in the same units before you divide. 1 mm = 1000 micrometres (µm).
Worked example
A cell is 0.05 mm long. In a drawing it is 40 mm long. What is the magnification?
- Magnification = image size ÷ actual size. Both are already in mm.
- = 40 ÷ 0.05.
- = ×800.
Tips and tricks
- Measure the image with a ruler in millimetres, and change the actual size into millimetres too.
- Magnification has no units. Write it as ×800.
It lands in your notebook with its questions as flashcards.
Magnification: 5 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
How is magnification calculated?
The image is bigger, so it goes on top.
An image is 50 mm long and the real object is 0.5 mm long. What is the magnification?
50 ÷ 0.5.
How many micrometres are there in 1 mm?
So 0.01 mm is 10 µm.
An image is 30 mm wide at a magnification of ×600. How wide is the real object?
30 ÷ 600.
What are the units of magnification?
It is one length divided by another, so the units cancel.
Quiz
5 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
3 questions, 6 marks. Write your answers on paper, then check them.
Magnification
Cambridge IGCSE Biology 0610 · 6 marks · papermunch.org
Name ______________________________ Date ______________
A drawing of a leaf is 120 mm long. The real leaf is 40 mm long. Calculate the magnification.[2]
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×3. 120 ÷ 40.
A photograph of a cell is 60 mm wide. The magnification is ×1500. Calculate the actual width of the cell in micrometres.[3]
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40 µm. 60 ÷ 1500 = 0.04 mm; 0.04 × 1000.
Convert 0.2 mm into micrometres.[1]
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200 µm.
Answers: Magnification
- 1. ×3. 120 ÷ 40.
- 2. 40 µm. 60 ÷ 1500 = 0.04 mm; 0.04 × 1000.
- 3. 200 µm.