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NCERT Solutions Curiosity Chapter 10 .3 What Are the Laws of Reflection? — Activity 10.5: Let us experiment

Book page 15910 Updated on2026-09-05

Q1.
Now, bend the extended part of the sheet along the edge of the table (Fig. 10.10b). Do you still see the reflected beam on the extended portion?
Answer

No. The moment the overhanging part of the chart paper is folded down along the edge of the table, the bright streak on it disappears.

Why it disappears: the reflected beam has not moved and has not switched off — it is still travelling in exactly the same direction, in the flat plane of the table. The folded-down paper has swung out of that plane, so the beam no longer lands on it. Nothing about the light changed; only the screen did.
Check it yourself: hold a sheet of paper flat, level with the table, just beyond the folded part. The reflected beam shows up on it again, proving the beam was there all along.
Q2.
Flatten the paper again and observe.
Answer

The reflected beam reappears on the extended portion, exactly where it was before.

This appearing-and-disappearing is the whole point of the activity. It shows that the reflected beam lies in one particular plane — the plane that also contains the incident beam and the normal — and nowhere else.

Second law of reflection:
The incident ray, the normal to the mirror at the point of incidence,
and the reflected ray all lie in the same plane.
Why the fold is a fair test: bending the paper creates a new plane at an angle to the old one. If the reflected light were free to leave the original plane, some of it would fall on the bent portion. Nothing lands there, so the light is confined to the original plane — which is precisely what the second law states.
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