What is Tyndall effect?
If a homogeneous solution in dark is observed in the direction of light, it appears clear and, if it is observed from a direction at right angles i.e. 90° to the direction of light beam, it appears perfectly dark.
Colloidal solutions (a heterogeneous solution in which one substance is dispersed in another substance.) viewed in the same way also appear reasonably clear or translucent by the transmitted light but they show a mild to strong opalescence when viewed at right angles to the passage of light, i.e. , the path of the bean is illuminated by a bluish light. This effect is known as TYNDALL EFFECT.
Cause of Tyndall Effect
The Tyndall effect is due to the fact that colloidal particles scatter light in all directions in space. This scattering of light illuminates the path of beam in the colloidal dispersion. The diameter of the dispersed particles particles should not be much smaller than the wavelength of the light used for Tyndall effect to occur.
Tyndall Effect in Daily life
1. Tyndall effect can be observed during the projection of picture in the cinema hall due to scattering of light by dust and smoke particles present there.
2. A mixture of milk and water appears blue when viewed by the reflected light and red when viewed by the transmitted light.
3. Human eyes that appear blue in colour do not contain any colour pigments in them. The Iris is made up of two layer, the stroma, and the epithelium. In case of blue eyes, stroma is translucent and contains no pigment. The white light is reflected by the stroma and gets scattered after undergoing reflection. The blue light has shorter wavelength and gets scattered more than any other colours.
4. Finest Gold sol is red in colour, as the size of particles increases, it appears purple, then blue and finally golden.
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