| English | Linear magnification |
|---|---|
| Bahasa Melayu | Pembesaran linear |
| 中文 | 线性放大率 |
Definition
The ratio of the height of the image to the height of the object, equal to image distance divided by object distance.
In exam terms
Linear magnification m is the ratio of the height of the image to the height of the object: m = image height ÷ object height. For a thin lens it equals the image distance divided by the object distance, m = v ÷ u.
It has no unit because it is a ratio.
If m is greater than 1 the image is enlarged; if less than 1 it is diminished; if equal to 1 it is the same size. For example, if v = 20 cm and u = 10 cm, then m = 20 ÷ 10 = 2, so the image is twice the object's height.
Do not confuse it with power of a lens
Do not confuse linear magnification with the power of a lens. Magnification describes how big the image is compared with the object; power (1 ÷ focal length, in dioptres) describes how strongly the lens bends light.
A lens has fixed power but the magnification changes with object distance.
In Paper 2, a calculate the magnification question expects m = v ÷ u (or image height ÷ object height), and you should also state whether the image is larger or smaller than the object.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)