The daytime sky appears blue mainly because of which optical phenomenon involving sunlight and atmospheric gas molecules?

1. Air molecules are much smaller than the wavelength of visible light, so Rayleigh scattering applies. 2. By $S' \propto \dfrac{1}{\lambda^4}$, shorter (blue) wavelengths scatter far more than red. 3. The scattered blue light reaches our eyes from all directions, making the sky look blue. 4. Mie scattering (option) governs white clouds, not the blue sky. _Source: Samacheer Kalvi (TN SCERT) Class 10 Science, Unit 2 Optics "Scattering of Light", p.25_