The Omega Sun_

In the picture you can see an example of the optical phenomenon known as “ Omega Sun”. The name is due to the apparent shape of the solar disk, similar to that of the Greek letter omega. In reality, what we see is the fusion of two images: the real image of the disk, slightly stretched vertically, and a portion of its mirror image ( and therefore upside down ) that forms the base of the omega. The phenomenon is due to the refraction of light, that is to say the deviation of the rays of light when they pass through layers of different substances having different refractive indices. In the case of the photo, taken at sunrise on a summer day, the sea, warmer than the air above, creates a thin layer of warmer and less dense air that causes the phenomenon.

The observation of the “ Omega Sun “ is not easy because it requires the simultaneous occurrence of three events: absence of clouds on the horizon, transparent air and, finally, a discrete difference of temperature between the sea and the atmosphere.

 

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