Foggy Morning on Portage Lake and the Tyndall Effect

Foggy morning, photo by Jiqing Fan

Wikipedia says that Portage Lake is part of the Keweenaw Waterway, a partly natural, partly artificial waterway that cuts across the Keweenaw Peninsula to provide access for shipping from Lake Superior. If you click the link you can get an aerial view.

View Jiqing Fan’s photo bigger and see more in his massive Houghton & UP MI slideshow. He writes:

Saw the fog on Lake Portage from my apartment window after I woke up today. I knew the potential this fog can bring so I darted down to the lake shore. But the fog was so heavy that the foliage on the other bank were completely blocked. Just when I was about to give up and head back for school, the fog started to break as the sun rises. And then the magic started to unfold before my eyes. Soon the fog lifted and fill the campus uphill, the entire campus was bathed in soft morning light and there were Tyndall effect everywhere! I can not think of a better way to start a day of work.

What’s the Tyndall effect you ask? The UC Davis ChemWiki explains that the Tyndall effect was identified by 19th Century Irish scientist John Tyndall.

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.

The Tyndall effect is an easy way of determining whether a mixture is colloidal or not. When light is shined through a true solution, the light passes cleanly through the solution, however when light is passed through a colloidal solution, the substance in the dispersed phases scatters the light in all directions, making it readily seen.

For example, light is not reflected when passing through water because it is not a colloid. It is however reflected in all directions when it passes through milk, which is colloidal. A second example is shining a flashlight into fog or smog; the beam of light can be easily seen because the fog is a colloid.

Yay science!

2 thoughts on “Foggy Morning on Portage Lake and the Tyndall Effect

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