NCERT Solutions Curiosity Chapter 10 .4 What Is a Lens? — In-text Questions

Book page 16310 Updated on2026-09-05

Q1.
What changes can be seen in the objects when viewed through lenses?
Answer

The object can change in size and, with a convex lens, even in orientation.

LensObject close to the lensObject taken far from the lens
ConvexErect and enlargedInverted — first enlarged, then getting smaller
ConcaveErect and diminishedStill erect, becoming smaller
Why a convex lens can flip the object but a concave lens cannot: a convex lens converges the light passing through it, so beyond a certain object distance the rays actually cross before reaching your eye — and crossed rays give an inverted view. A concave lens only ever spreads the rays out; they never cross, so what you see can never be upside down.
Q2.
Do lenses also converge or diverge the light beam?
Answer

Yes. A convex lens converges a parallel beam of light and a concave lens diverges it — which is why they are also called a converging lens and a diverging lens. Activity 10.10 shows both.

Why the two shapes behave oppositely: a ray is bent more where the two faces of the glass are more steeply slanted to each other. In a convex lens the glass is thickest in the middle, and its faces slope inwards as you go outwards from the centre, so the outer rays are pushed inwards and the beam closes on a point. In a concave lens the glass is thinnest in the middle and the faces slope the other way, so the outer rays are pushed outwards and the beam opens up.
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