Tyndall Effect

Introduction

The Tyndall Effect is the effect of light scattering in many directions in colloidal dispersion, while showing no light in a true solution. This effect is used to determine whether a mixture is a true solution or a colloid. "To be classified colloidal, a material must have one or more of its dimensions (length, width, or thickness) in the approximate range of 1-1000nm."

Because a colloidal solution or substance (like fog) is made up of scattered particles (like dust and water in air), light cannot travel straight through. Rather, it collides with these micro-particles and scatters causing the effect of a visible light beam. This effect was observed and described by John Tyndall as the Tyndall Effect.

Why is the Sky is Blue?

We know that blue light has the shortest wavelength in the visible light spectrum, while red has one of the longest. We also know that light with shorter wavelengths scatters more so than longer wavelengths. Thus, the sky looks blue when viewed away from the sun: the blue light is scattered more and is visible to a greater extent.

References

1. Heidorn, Keith PhD. The Weather Doctor's Weather Almanac: John Tyndall. NASA 2006
2. John Tyndall (1896). The Glaciers of the Alps. Longmans, Green and Co.. Republished as Tyndall, J. 1860 (2005). The Glaciers of the Alps. Adamant Media Corp.
3. Petrucci, Ralph, William Harwood, F. Herring, and Jeffry Madura. General Chemistry: Principles and Modern Applications 9th Ed. New Jersey, 2007.

Contributors

• Bella Mody (UCD)

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