Kōrero: Atmosphere

The shadow length rule

The shadow length rule

The most important factor controlling UV radiation is the sun's angle above the horizon. At low angles, the sun's rays pass through much more of the atmosphere, reducing the radiation. As a rule of thumb, if the length of your shadow is more than twice your height (when the angle of the sun is less than 30°), then the UV Index will generally be less than 3 (UVI 'low'), and there is little risk of UV damage. If your shadow is less than twice your height, some protection may be needed. If your shadow is less than your height (the sun's elevation is greater than 45°), the UV Index can exceed 7 (UVI 'very high'), and protection is required.

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Te Ara - The Encyclopedia of New Zealand

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Te tuhi tohutoro mō tēnei whārangi:

Bill Allan, Katja Riedel, Richard McKenzie, Sylvia Nichol and Tom Clarkson, 'Atmosphere - Ozone and ultraviolet radiation', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/mi/diagram/6157/the-shadow-length-rule (accessed 25 February 2020)

He kōrero nā Bill Allan, Katja Riedel, Richard McKenzie, Sylvia Nichol and Tom Clarkson, i tāngia i te 12 Jun 2006