Scattering — Blue SkyMediumQuestion 20225
Question
The sky appears blue because:
- AAir molecules absorb red light
- BRayleigh scattering ∝ 1/λ⁴ scatters shorter (blue) wavelengths more intenselyCorrect
- CWater vapour reflects blue light
- DOzone absorbs red wavelengths
Correct answer
Rayleigh scattering ∝ 1/λ⁴ scatters shorter (blue) wavelengths more intensely
Explanation
Rayleigh scattering intensity ∝ 1/λ⁴. Blue light (λ ≈ 450 nm) is scattered ≈5–6× more than red light (λ ≈ 700 nm). Scattered blue light reaches us from all directions — the sky appears blue. At sunset, the direct path is longer, blue is scattered away, and red/orange dominates.