How The Tyndall Effect Is Responsible For Blue Eye Colour

The Iris is the coloured component of the eyes, and it consists of two layers – the epithelium at the back and the stroma in the front. The epithelium is made up of two thick cells that contain brown-black pigments; the dark specks in some people’s eyes are the epithelium peeking through. The stroma, on the other hand, is made up of colourless collagen fibres.

The stroma may include a dark pigment called melanin, or it may have excessive collagen deposition. But it is the combination of these two factors that determine the colour of your eyes. Brown eyes, for instance, have a high melanin concentration in the stroma of their eyes, which absorbs the majority of the light beam that enters the eye, independent of collagen deposition, thus, resulting in their dark colour.

Green eyes have no melanin, but they also have no collagen deposits.

This means that while some of the light that enters the eye is absorbed by a pigment, the stroma’s particles scatter light, resulting in blue colour and the Tyndall Effect (similar to Rayleigh scattering, which causes the sky to seem blue). When this is paired with brown melanin, it causes the eyes to seem green. Because blue eyes are fully structural, they have the most intriguing potential. Blue eyes have a stroma that is entirely colourless and has little collagen deposition. All of these result in light entering the environment and being dispersed in the atmosphere, reflecting the colour blue as represented by the Tyndall Effect.

This implies that blue eyes do not have a set colour; their colour is determined by the amount of light available when you gaze at them.

Tyndall Effect

Technically, the Tyndall Effect is defined as the dispersion of sunlight as a light beam travels through a Colloid. Whenever the light goes through a solution of colloidal, it gets scattered and reflects where the beam becomes visible. In the Tyndall effect, blue light is scattered more than red light, in contrast to the Rayleigh Scattering. The sky’s blue colour is created by light scattering as well; however, this scattering is known as Rayleigh Scattering and is not caused by the effect of Tyndall. It happens due to the involvement of the particles in the molecules scattering in the air. The particles that result in the appearance of the Tyndall effect in the colloidal form turn out to be larger than these air molecules. When we stare at the blue water, it appears blue. Rather than the existence of blue pigments in our oceans, this is due to light scattering. 

This is referred to by scientists as Structural Colouring, and it is not the same as pigment colouring. When you see blue or blue goods in nature, they are blue due to structural colouring and do not include any blue colours or blue pigments.

Tyndall Effect Causes

In a real solution, the colloidal particle is larger than the solute particle. Colloidal particles absorb light energy and scatter some of it off their surfaces. Thus, the Tyndall effect is created by colloidal particle light scattering, and the colloidal particles can be seen moving as points of light on a black backdrop.

Why Does The Sky Not Appear Violet?

If different wavelengths were mostly heavily scattered, why does the sky not appear violet, the colour with the shortest visible wavelength? The sun’s light spectrum is not continuous throughout all wavelengths, and it is also reduced by the earth’s atmosphere, leading to less violet light.

In addition, our eyes are less sensitive to violet. That is part of the answer; nevertheless, a rainbow shows that there are still considerable amounts of light waves coloured indigo and violet that are farther than the blue. The remainder of the solution to this dilemma may be found in how human eyesight works. There are three types of colour sensors, or cones, in the human retina. They’re called red, blue, and green because they’re the most sensitive to light at those wavelengths. Our visual system generates the colours we perceive by activating them in varying amounts.

Conclusion

Short-wavelength blue light is dispersed more strongly than long-wavelength red light, as in Rayleigh scattering. Rayleigh scattering happens from particles that are considerably smaller than the wavelength of light, whereas the Tyndall effect occurs from particles that are nearly the same size as the wavelength of light. The Tyndall effect is named after the 19th-century British scientist John Tyndall.