Question

Why do clouds appear white while sky appears blue?

Answer 1

Scattering of light depends on the size of particles responsible for scattering. The droplets in the clouds are big compared to the wavelength of light, so light of all wavelengths are scattered equally and hence clouds appear white. Earth's atmosphere is made up of gases, whose size is comparable to the wavelength of visible lights. The smaller the wavelength more the scattering of light. The sky is blue because molecules in the air scatter blue light from the sun more than they scatter red light.