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3.6.3Stoichiometry

Magnification — Cambridge IGCSE Chemistry 0620 Revision Notes & Topical Questions

5 min read 5 parts Lesson 14 of 28 Unit quiz

📚 Cambridge IGCSE Chemistry 0620 Hub / Topical Revision
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Section 1 of 5The Magnification Equation

Magnification compares the size of the image with the size of the object.

Definition
  • Definition Magnification is the image height divided by the object height, so it tells how many times larger the image is than the object.
No units
  • No units Magnification is a ratio with no units, so the object and image heights must be measured in the same unit before dividing.
Magnified
  • Magnified A magnification greater than 1 means the image is larger than the object.
Diminished
  • Diminished A magnification less than 1 means the image is smaller than the object, as happens for a distant object seen through a camera lens.
Object heightImage heightMagnificationImage size
4.0 cm10.0 cm2.5Magnified
4.0 cm2.0 cm0.5Diminished
4.0 cm4.0 cm1.0Same size

Section 2 of 5Rearranging the Equation

1
Write the equation as magnification = image height ÷ object height, and substitute the known values with the same units.
2
To find an image height, multiply the magnification by the object height.
3
To find an object height, divide the image height by the magnification.
4
Check the answer by confirming that a magnification above 1 gives an image taller than the object.

Section 3 of 5Factors Affecting Magnification

Factors Affecting Magnification
Object distance
  • Object distance Moving the object closer to a converging lens, within its focal length, increases the magnification of the image formed.
Lens power
  • Lens power A stronger lens with a shorter focal length gives a greater magnification for the same object distance.
Measuring
  • Measuring Measure both heights from the same scale drawing or photograph, using the same ruler units throughout.
Accuracy
  • Accuracy Measure the image height at its widest point, and check that the object height is measured at the same scale.

Section 4 of 5Worked Example

Question

  • A magnifying glass forms an image of a 4.0 cm long insect.
  • The image is 10.0 cm long.
  • Calculate the magnification and state whether the image is magnified.

  1. Step 1: Write magnification = image height ÷ object height.
  2. Step 2: Substitute the values with the same units: 10.0 cm ÷ 4.0 cm.
  3. Step 3: Calculate 10.0 ÷ 4.0 = 2.5, with no units.

Answer The magnification is 2.5, so the image is magnified.

Section 5 of 5Exam Checklist & Tips

3.6.3 – Key Points for the Exam

  • Magnification The ratio of image height to object height, with no units.
  • Image height The height of the image, measured in the same unit as the object height.
  • Object height The height of the object being imaged, measured in the same unit as the image height.
  • Magnified image An image with a magnification greater than 1.
  • Diminished image An image with a magnification less than 1.

Common Mistakes

  • Dividing the object height by the image height, which gives the reciprocal of the magnification.
  • Using mixed units, such as centimetres for the image and millimetres for the object, without converting first.
  • Giving magnification a unit such as cm, when it is a ratio with no units.
  • Stating that a magnification of 0.5 means the image is magnified; it means the image is diminished.

Last updated:

Cambridge 9700 AS Biology Core Formula

Magnification Triangle & Unit Conversion

Formula: M = I / A  ⇔  A = I / M  ⇔  I = M × A

Units: 1 mm = 1,000 μm = 1,000,000 nm.
Rule: Convert Image size (ruler mm) to μm by ×1,000 before dividing by Actual size.

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