Question 7
Observe what happens to the size of the shadow as you vary the distance between your torch and your object.
The size of a shadow changes based on the distance between the light source and the object.
Step 1 — Setting up the experiment
Let us set up a simple experiment. We need a torch, an object, and a screen. Place the object between the torch and the screen. The torch acts as our light source. The object blocks the light rays. This creates a shadow on the screen.
Step 2 — Observing shadow size
Let us first place the torch far from the object. Observe the size of the shadow on the screen. Now, let us move the torch closer to the object. We keep the object and screen in place. Observe the shadow's size again.
Step 3 — Drawing a conclusion
When the torch is moved closer to the object, the shadow becomes larger. When the torch is moved farther from the object, the shadow becomes smaller. This happens because light rays spread out more from a closer source. So, a closer torch casts a wider shadow. A farther torch casts a narrower shadow.
Answer
The size of the shadow increases as the torch moves closer to the object. Conversely, the size of the shadow decreases as the torch moves farther from the object.
More questions in A
Build it in Your Imagination
We will start this section by practising visualisation. For each prompt, feel free to talk to your partner, gesture, draw it in the air — but do not actually draw on paper!
- Picture your name, then read off the letters backwards. Make sure to do this by sight, not by sound — really see your name! Now try with your friend's name.
Cut off the four corners of an imaginary square, with each cut going between midpoints of adjacent edges. What shape is left over? How can you reassemble the four corners to make another square?
Mark the sides of an equilateral triangle into thirds. Cut off each corner of the triangle, as far as the marks. What shape do you get?
Mark the sides of a square into thirds and cut off each of its corners as far as the marks. What shape is left?
Net of a sphere? Experiment and see if you can make a paper cutout that can perfectly wrap around a ball without leaving any wrinkles, gaps or overlaps.
Place an object in front of a plane, such as a wall of your room. Shine a torch light on the object in a direction perpendicular to the wall.
What do you see?
Observe what happens to the size of the shadow as you vary the distance between your torch and your object.
Context: Observe what happens to the size of the shadow as you vary the distance between your torch and your object.
Q. Why does this happen?
Construct a model of a cube and use your hands to keep it balanced on one corner vertex. Can you try to understand why all the projected edges have equal length?