What happens when an opaque object blocks the path of light?
Answer
The light is stopped, and a shadow is formed on the screen behind the object.
The shadow is simply the region of the screen that receives no light. Around it the screen stays bright, because there the straight rays from the source arrive without hindrance.
Tip: A shadow always has the same outline as the object seen from the side of the light source — never its colour and never its details.
Q2.
What did you see on the screen in Activity 11.3 when an opaque object was placed in the path of light? Did you see a dark patch on the wall? Why was this dark patch formed?
Answer
On the screen we saw a dark patch shaped like the object, surrounded by the lit part of the screen. Yes, this dark patch was seen on the wall.
The dark patch was formed because light travels in a straight line. The opaque object stopped every ray that was heading for that part of the wall. Since light cannot bend around the object to fill in the gap, that part of the wall stayed dark — and a dark patch of this kind is called a shadow.
Why it happens: Think of the rays as straight arrows shot from the torch. The arrows that miss the object hit the wall and light it up; the arrows aimed at the object are caught by it. The wall is dark exactly where the object's outline stands in the way.