UV spectra to produce vitamin D
The vertical access is a log scale, so it is very difficult to get enough vitamin D via skin (dotted line) when the solar zenith angle (SZA) is greater than 75 degrees
The graph also indicates that the amount of vitamin D from UV decreases by 10X when the wavelength is 310 nm and down by 100X (virtually non-existant) when the wavelength is 320 nm
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