[Jonathan Wesley Daugherty]

Jonathan Wesley Daugherty asked the Naked Scientists:
What is the Tyndall effect, and what causes it?
What do you think?

[chris]

This is named in honour of the Irish scientist John Tyndall who noticed that fine particles scatter light, but that the shorter wavelengths of light (i.e. blue) are more scattered than longer (redder) wavelengths. Consequently, this explains why the sky is blue. It's because the light from the Sun comprises a mixture of wavelengths of light, including blues, greens, yellows and reds, which together look white. When the sunlight hits the Earth's atmosphere the oxygen and nitrogen molecules scatter the shorter blue wavelengths much more than the longer red wavelengths, because the wavelength of the blue light is closer in size to the gas particles than the red light, which is affected much less.

As a result blue light rays are bounced about all over the sky and so when you look upwards your eyes see blue light arriving from all directions, so your brain thinks that the sky must be blue. We know this isn't true because stars seen at night look white - i.e. the unlit sky is colourless.

So why do we see a red sunset? It's because as the sun sinks towards the horizon its light must pass a greater distance through the atmosphere before it reaches you making the scattering effect even more pronounced. As a result even more of the blue an some of the green light is scattered, leaving the remain light rays reaching your eyes looking much more red.


Chris

[lyner]

See Rayleigh Scattering

[Jonrio]

thank you that will help me a lot in chemistry

Jonathan Wesley Daugherty [|)]

[lyner]

thank you that will help me a lot in chemistry

Jonathan Wesley Daugherty [|)]

Was that OK, then? Do you see the relevance to Chemistry? Presumably you are talking about colourimetry?

[JimBob]

WARNING - Tongue in cheek reply follows: disregard if science content is needed.

It is being caught up in rapture and the light of a spiritual experience when one first picks up his Bible and reads it.