Sun, Sky and Cloud: Where light and matter meet

Textbooks focus first on the reflection and refraction of light, and later on individual events of emission, absorption, and scattering. In Nature, it often happens that we see light which has undergone these processes many times, sunlight passing through clouds is just one example, related phenomena occur on the visible surfaces of the Sun and stars. The intensity and angular distribution of the light we see tells us not only about the source but also the medium through which it has passed to reach us. This area of science is known as radiative transfer. Its basic features are illustrated in this article, along with some examples. © 2015, Indian Academy of Sciences.