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Showing 1 question in Physics for Class 10. Tap a card to reveal the answer.
PhysicsThe Human Eye and the Colourful WorldmediumWhy does the clear sky appear blue?
Reveal answer ↓
What it is
The sky is blue because tiny air molecules scatter blue light much more than red.
Answer
Sunlight is scattered by the tiny molecules of air in the atmosphere. Blue light has a shorter wavelength and is scattered much more strongly than red light. As this scattered blue light reaches our eyes from all directions, the clear sky appears blue. At sunset the light travels a longer path, most of the blue is scattered away, and the remaining red light makes the sky look reddish.
- •Air molecules scatter sunlight
- •Blue (shorter wavelength) scatters most
- •Scattered blue reaches our eyes -> blue sky
- •Sunset: blue scattered away, red remains
Why learn this
The same scattering explains red sunsets and why danger signals are red (least scattered).
💡 Memory trick
Blue scatters most (short wavelength), so the sky looks blue; at sunset the long red light survives.