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Thursday, July 10, 2008

Coloured hoop

You will certainly only have seen a rainbow in the sky as a semi-circle up to now. You can conjure up a complete circle for yourself from sunlight. Stand out-of-doors on a stool in the late afternoon with your back to the sun and spray a fine shower with the water hose. A coloured circle appears in from of you! The sunlight is reflected in the
drops so that each shines with the spectral colours.

But the colours of the drops are only visible to your eyes when they fall in a circular zone at a viewing angle of 85 deg. in front of you. Only the shadow of your body briefly breaks the circle.

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