Scattering Of A Beam Of Light

Have you ever wondered what happens when a beam of light is passed through a solution?

A solution is characterized by the density of colloidal particles seen in it. A true solution is determined by its ability to pass the light through it. The size of the particles is the distinguishing factor from a colloidal solution with a true solution. For a mixture to be colloidal, the particles must be in the range of 1-1000 nanometers in diameter.

Tyndall effect is the phenomenon in which the particles in a colloid scatter the beams of light that are directed at them. The intensity of scattered light, when passed through a solution, depends on the density of the colloidal particles as well as the frequency of the incident light. Tyndall effect can be briefly explained as the condition in which light beam becomes illuminated or visible when passed through a colloidal solution kept in a dark room. Tyndall effect is also known as Willis–Tyndall scattering.

Let us verify how the Tyndall effect comes into the picture by passing a beam of light passes through a colloidal solution. The colloidal particles present in the solution do not allow the beam to easily pass the light beam through it. The light when collides with the colloidal particles is scattered. Normally the light passes as a straight line deviates from its normal trajectory when it collides with the particles. This scattering makes the path of the light beam noticeable, as shown in the figure below.

Scattering also depends on the wavelength of the light. Blue color light is scattered to a greater extent when compared to red color light. Clear sky is blue in color due to the scattering of light by air particles, which is an example of Rayleigh scattering.

Some of the known examples to justify the Tyndall effect are:

  • When a torch is switched on in a foggy environment, the path of the light becomes visible. In this scenario, the water droplets in the fog are responsible for the light scattering.
  • Milk is a colloid since it has globules of protein and fat. When a beam of light is passed through a glass of milk, the light is scattered.
  • Opalescent glass has a bluish appearance when viewed from the side. However, orange-colored light emerges when light is shined through the glass.

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