Texas Math And Science Coaches Association (TMSCA) Science Practice Exam

Sunlight is made of a mix of colors, but as it travels through the air, the gas molecules scatter light. When the scattering depends on wavelength, shorter wavelengths scatter much more strongly than longer ones. This is Rayleigh scattering. Because blue light has a shorter wavelength, it gets bounced in many directions by air molecules, so the sky looks blue from everywhere you look. Violet light is scattered even more, but there’s less violet reaching us from the Sun and our eyes are more sensitive to blue, so the sky doesn’t appear violet. If larger particles were responsible, a different kind of scattering would happen that tends to produce a whiter, less blue sky (Mie scattering). Diffraction isn’t the main effect here, and fluorescence involves light being absorbed and re-emitted, not just scattered in the atmosphere, so it doesn’t explain the blue sky.