NCERT Solutions for Class 8th Science Chapter 10 .1 What Are Spherical Mirrors? — Activity 10.2: Let us distinguish
Book page 15510 Updated on2026-09-19
Q1.
Now view them from the side, keeping your eye at their level, to identify whether the reflecting surface is curved inwards or outwards (Fig. 10.4).Fig. 10.4, page 155 — the two mirrors lying face up on the table, seen from the side with the eye at their level. Redrawn sketch: the concave mirror’s shiny face is hollowed inwards, the convex mirror’s bulges outwards.
Answer
Looking along the surface, edge-on, the shape shows up at once:
If the shiny surface dips down in the middle — the edges stand higher than the centre — it is a concave mirror.
If the shiny surface rises in the middle — the centre stands higher than the edges — it is a convex mirror.
Seen edge-on, the difference is obvious: the shiny side of a concave mirror is hollowed inwards; the shiny side of a convex mirror bulges outwards. The shaded part is the non-reflecting back.
Why the eye must be at surface level: from directly above, both mirrors look like flat silver discs, because you are seeing the surface face-on and the small rise or dip is hidden. Bringing the eye down to the level of the mirror lets you see the profile of the surface against the background, and a difference of even a millimetre becomes visible.
Check it yourself: without moving the mirrors you can confirm the answer a second way — put a small object 3–4 cm in front of each. The mirror that enlarges it is concave; the one that shrinks it is convex.