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Section 3 - Rayleigh Dispersion


If we go deep in the phenomena related to the blue sky nature, we have to study the interaction between light and particles of small size, the so-called Rayleigh Dispersion.

Normally, when any electromagnetic wave (such as sunlight) finds in its trajectory an atom (or a small molecule), it interacts with its cloud of electrons, transmitting energy to the atom. This causes that the atom lowest level of energy (the natural state) begins to vibrate.

The oscillating electrons do not keep on vibrating for a long time. They return to the initial state by irradiating some of the energy they have got. Lord Rayleigh studied the dependence between the amount of irradiated light and the light wave length. He set up that the quantity of irradiated light is inversely proportional to the fourth power of the wave length. It can be represented as:

Therefore, if the incident light is white (an addition of different wave lengths or colours), the irradiated light will contain a higher amount of colours with shorter wave length (blue and violet) and less amount of colours with longer wave length (yellow and red). So we came out to the same conclusion than in the previous section.
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