The appearance of a rainbow is always a special sight, marveling both children and adults. How does this optical and meteorological phenomenon form?
If rainbows are so fascinating, it’s both for their beauty, but also because a rainbow contains a continuous transition of colors. That is to say that there are as many colors as what the eye can distinguish, that is to say at most 150. It is a colored arc with always red on the outside and purple on the inside .
This optical and meteorological light phenomenon occurs whenever drops of water fall or are suspended in the air and a light source shines behind the observer. This meeting of the light source and the water suddenly makes the spectrum of light perceptible.
The light coming from the sun reflects on the drops of water at an angle of approximately 40°. This is not quite characterized as a mirror, since in this case the reflection of the sun itself would be observed, but rather as a prism which refracts white light into a multicolored spectrum.
Why can’t we ever get to the bottom of a rainbow? For the phenomenon to be visible, the person observing the rainbow must be located between the sun, behind it, and the top of the arc, opposite. Thus, this alignment constraint must be perfectly respected in order to be able to observe the luminous phenomenon. Impossible then to go to the foot of a rainbow, the movement of the observer causing the displacement also of the latter.
A rainbow therefore has no material existence, but is a purely optical effect whose apparent position depends on those of the observer and the Sun. The center of the rainbow is in the exact opposite direction from the Sun relative to the observer.