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I have captured for La Vanguardia Readers' Photos these snapshots of the sky of L'Escala, in Alt Empordà, with a sky marked by spectacular clouds that, through them, the sun has produced a colorful effect.
In the photographs the phenomenon of the solar halo and iridescence come together. The halo forms around the sun, presenting an iridescent ring on its outer circumference, due to ice crystals when there are high clouds.
The halo is caused by ice particles suspended in the troposphere that refract light, generating a spectrum of colors around the Moon or Sun.
It is, therefore, an optical effect in the shape of a disk around the sun - or the moon - and which has an iridescent ring on its outer circumference.
Iridescence is caused by multiple reflections of light from multiple semitransparent surfaces, where subsequent phase changes and interference of the reflections modulate the light by amplification or attenuation of different wavelengths.
Depending on the angle at which the surface is illuminated, it will look different colors. Iridescence is very common in nature, we can easily see it in insects, birds and fish, and even in plants.
Iris, in Greek mythology, is the personification of the rainbow and messenger of the gods, who left a trail of luminous colors behind her.
