(a) When a ray of light passes through the centre of curvature (C) of a concave mirror, it reflects back along the same path. But a ray directed towards the focus (F) reflects parallel to the principal axis.
Ray Diagram:
```
C F P
------------* ------→ (reflected ray, parallel to PA)
\ ↗
\/
(incident ray aimed at F)
```
(Label: C = Centre of curvature, F = Focus, P = Pole, PA = Principal Axis)
(b)(i)
| Feature | Convex Mirror | Concave Mirror |
|---|---|---|
| Size of virtual image | Always diminished | Always enlarged |
| Object position | Any position | Between pole and focus |
(b)(ii)
Given: m = –2, height of image (h′) = 20 cm
$$m = \frac{h'}{h} \Rightarrow -2 = \frac{20}{h} \Rightarrow h = \frac{20}{-2} = -10 \text{ cm}$$
Height of object = 10 cm (negative sign indicates object is real/upright as per convention).
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