NCERT Solutions for Class 5th The World Around Us Chapter 7 Sunlight in Focus — Activity 7
Book page 124 Updated on2026-09-19
Q1.
Sunlight in Focus — 1. Take a piece of paper and a magnifying glass. 2. Place the paper in direct sunlight and use the magnifying glass to focus the light on it. Tip: The activity has to be done under adult supervision.
Answer
How to do it — only with an adult standing beside you:
Choose an open, sunny spot outdoors. Stand on stone or bare ground, never on grass or near paper, cloth or dry leaves.
Keep a mug of water beside you before you begin.
Lay a small piece of paper flat on the ground or on a stone. A dark or newspaper piece works best.
Hold the magnifying glass between the Sun and the paper.
Move the glass slowly up and down. You will see a circle of light on the paper. It grows bigger and smaller as you move.
Stop when the circle is at its smallest and brightest — the size of a dot. That dot is the focus, the point where all the light is gathered.
Hold the glass steady there and watch the dot.
The lens gathers a wide beam of sunlight into a single small spot.
Safety rules, and they matter: Never look at the Sun through the glass — it can damage your eyes. Never point the hot dot at anyone's skin, clothes or hair. Do it on bare ground, with an adult and water at hand, and put the glass away face down when you finish so it cannot start a fire by itself.
Q2.
3. What happens to your paper?
Answer
The paper grows very hot at that one bright dot. It turns brown, then black, then starts to smoke, and if you hold the glass steady it catches fire and burns a small hole.
Time
What happens at the dot
At once
A very bright small spot appears
After a few seconds
The paper turns brown at that spot
A little later
The brown mark turns black and a thin thread of smoke rises
If held steady
The paper catches fire and a small hole burns through
Why it happens: Sunlight carries heat. Spread over a whole page, that heat only makes the paper pleasantly warm. The magnifying glass bends all the light that lands on it and gathers it into one tiny dot. Now the heat that was spread over the whole lens is packed into a spot smaller than a grain of rice. Squeezed into that tiny place, the heat becomes strong enough to burn the paper. Nothing was added — the same sunlight was simply concentrated, that is, gathered into one place.
The same idea, put to work: a solar cooker uses shiny sheets to gather sunlight into the pot, and cooks dal and rice with no fuel at all. Bigger solar plants use rows of mirrors to gather sunlight and make steam. The Sun gives more energy to Earth in one hour than all the people on Earth use in a whole year.