Ever wondered about the reason for the light from the edge of clouds or from windows
in your darkroom or the beautiful sunlight coming through trees or the blue color of
smoke from your motorcycle engine or the blue color of the sky? These mesmerizing
phenomena are known as the Tyndall effect.
To understand the Tyndall effect, we need to know about colloid and suspension.
A mixture of solid in a liquid where the solid is evenly dispersed and does not undergo
sedimentation. The solid is the dispersed phase whereas the liquid is the dispersion
medium. The size of particles ranges from 1 nm- 1000 nm and are invisible to naked
eyes. Such a homogenous mixture is called colloid. Some examples of colloid: Dust,
fog, etc.
A mixture of solid in a liquid where the solid is insoluble in liquid but will eventually settle
at the bottom. The solid is the dispersed phase whereas the liquid is the dispersion
medium. The size of particles ranges between 0.5um to 5 um and are visible to naked
eyes. Such a heterogeneous mixture is called suspension. One example for suspension
is muddy water. So after knowing about the colloid and suspension, it is easier to
understand Tyndall effect
The effect of light scattering through a colloid when a beam of light is passed through it
is called the Tyndall effect. A colloidal solution or substance such as fog is made of
scattered particles. When light is passed through such a substance, it colloids with the
particles like water and dust in the air. Due to this collision, the beam of light is scattered
causing the effect of a visible light beam. John Tyndall who was a British physicist was
the first to describe this effect in the 19th century.
An example of the Tyndall Effect:
When you travel in the car, sometimes you will not be able to see far because of the fog
and the car headlights are not able to shine all the way through the fog. This is due to
the Tyndall effect. Fog is a colloidal substance. From above we already know that when
a beam of light comes in contact with scattered particles like fog and dust it undergoes
dispersion which leads to scattering of light in multiple directions. Hence the Tyndall
effect.
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