Why do shadows cast by tall buildings under direct sunlight have clean, straight edges?

Why do shadows cast by tall buildings under direct sunlight have clean, straight edges?
  1. Air particles bend sunlight toward the edges
  2. Sunlight travels in straight lines and cannot curve around solid structures
  3. Buildings act like giant mirrors reflecting rays away
  4. Sunlight cools down as it approaches concrete walls

Solution

Because light travels strictly in straight lines, it cannot bend around opaque obstacles, producing sharp boundaries along the shadow edges.

Asked in: Homi Bhabha Practice

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