I made a rough calculation (probably having made a miscalculation though) following here and here to find out the number of air molecules in 1 cubic centimetre of air. The first website says there are about 0.02504 x 10²⁷ air molecules in 1 cubic metre. The second one says the diameter of an air molecule is about 4 x 10⁻¹⁰m. Then the area of the molecule is about 4π x 10⁻²⁰, approx 12 x 10⁻²⁰. Then we get the number of air molecules in one cubic metre to be about 12 x 0.025 x 10⁷, and in one cubic centimetre to be about 12 x 0.025 x 10⁵ = 30000. So if there are 30000 air molecules in 1 cubic centimetre, it's almost impossible for light to miss hitting all of them. Following this logic, I can't comprehend how light propagates in air (I would expect it to be scattered, absorbed etc). How does physics explain this? Furthermore, since the speed of light in a vacuum is constant, but light is "slower" in higher refractive index materials, can I assume light travels a longer path when it travels through a medium with a refractive index higher than empty space? If not, What decreases its speed? (I thought two questions are related as they both question how light travel in air.)