The Atmosphere

The Ozone Layer

What is the Umkehr effect?

Swiss astronomer Paul Götz published a paper in 1931 in which he described how ultraviolet light is affected by the ozone layer. Ozone absorbs different wavelengths of light in the ultraviolet range at varying amounts, and these amounts change depending on the angle of the Sun in the sky (“umkehr” is German for “change” or “convert”). Measuring the difference between the amount of light being received at the two wavelengths can tell scientists how much ozone is in the atmosphere.


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