A shadow on the wall whose shape is very close to the projection of the object on that wall — but usually larger , and sometimes stretched or slightly distorted. Projection Torch shadow Rays Parallel and perpendicular to the wall Spreading out from one point Size Same size as the object’s outline Bigger than the object Shape Exact Similar, but stretched if the object is tilted

NCERT Solutions Ganita Prakash (Part 2) Chapter 4 Shadows — In-text Questions

Book page 94 Updated on2026-09-05

Q1.

What do you see?

Answer

A shadow on the wall whose shape is very close to the projection of the object on that wall — but usually larger, and sometimes stretched or slightly distorted.

	Projection	Torch shadow
Rays	Parallel and perpendicular to the wall	Spreading out from one point
Size	Same size as the object’s outline	Bigger than the object
Shape	Exact	Similar, but stretched if the object is tilted

Q2.

Observe what happens to the size of the shadow as you vary the distance between your torch and your object.

Answer

Bring the torch closer and the shadow grows; move it back and the shadow shrinks, settling down towards the size of the object’s outline and never getting smaller than that.

Torch at 20 cm from an object 40 cm from the wall → a big, blurred shadow
Torch at 2 m → a shadow only a little larger than the object
Torch very far away → the shadow becomes the projection

Check it yourself: if the torch is at distance d from the object and the wall is D behind the torch, the shadow is enlarged by the factor D⁄d. Doubling d roughly halves the enlargement.

Q3.

Why does this happen?

Answer

Because the light leaves the torch as a cone of spreading rays, not as a parallel beam.

Every ray that grazes the edge of the object carries on and lands further out on the wall. The closer the torch is to the object, the more steeply those edge rays are spreading, and the further out they land — so the shadow is bigger. Pull the torch back and the rays reaching the object are much more nearly parallel, so the outline they carve out on the wall is much closer to the object’s true outline.

Why the Sun makes a perfect projection: the Sun is about 15 crore km away. By the time its rays reach us they are, for all practical purposes, parallel. So when sunlight falls perpendicular to a wall, the shadow it casts is the projection — same size, same shape. That is why the book says you can settle the question about the parallelogram by taking a cardboard cutout outside and looking at its shadow.

Did you know? This is also why your shadow at noon is short and sharp but long and fuzzy near sunset, and why the shadow of a hand held near a wall is crisp while one held near the torch is huge and blurred.

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