Blue eyes are caused by the Tyndall Effect.

 

Solution:

Concept: The amount of melanin in one of the layers of the iris is the main distinction between blue, brown, and black coloured irises. When compared to a black iris, the layer in a blue iris contains relatively less melanin, which makes it translucent. The Tyndall effect causes light to be scattered when it strikes this translucent layer.

Blue light is more widely scattered than red light because it has a shorter wavelength. Unscattered light is absorbed by a deeper layer in the iris. These irises acquire their distinctive blue color because the majority of the scattered light is blue.

The scattering of light is a factor in numerous phenomena. Examples of such phenomena include Mie scattering and Rayleigh scattering. The reason the sky is blue in a clear day is because air molecules scatter light, which is a type of Rayleigh scattering. The scattering of light, a type of Mie scattering, occurs when the sky is cloudy and is caused by the relatively large cloud droplets.