Lesson 7 of 14
Why a wall shows you nothing
Show on a big screenA pond with no waves shows the temple upside down. The water is flat. Throw in one stone, and the picture turns wavy.
Step 1 of 4
- Top: a smooth surface. Bottom: a rough one.
- On the smooth surface, parallel rays (side by side) stay parallel.
- The rough surface is many tiny tilted patches.
- Each patch sends its ray a different way. They scatter.
The new word
- Scatter — light leaving in many directions at once.
The rule
A smooth surface reflects light all one way. A rough surface tilts each patch differently. So light , and no picture survives.
A wall reflects light too. That is how you see the wall. Up close, a wall has tiny bumps, each facing its own way.
Now try it. Roughen the surface. Watch the rays.
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Try the lab to finish this lesson.