Dr. Roger Sehault M.D. is a progressive doctor who posts many helpful articles. He is big on safe Sun exposure. The spectrum of energy from the sun is quite big, we know the visible light spectrum and we know about UV. However, there are many other spectrums that seem to be help.
By the way, there are 3 spectrums of UV which are UVA, B and C. I believe that it is UVB that is potentially harmful in higher exposure time.
https://actionservicesgroup.com/blog/which-uv-wavelength-is-most-dangerous-uva-uvb-or-uvc/
Of interest, UV spectrums are germicidal. NASA did studies on the use of red and near infrared and found that the light stimulated the cells for healing. During the Spanish flu, clinics were known to put the patients in the sun.
By the way, there are 3 spectrums of UV which are UVA, B and C. I believe that it is UVB that is potentially harmful in higher exposure time.
https://actionservicesgroup.com/blog/which-uv-wavelength-is-most-dangerous-uva-uvb-or-uvc/
Of interest, UV spectrums are germicidal. NASA did studies on the use of red and near infrared and found that the light stimulated the cells for healing. During the Spanish flu, clinics were known to put the patients in the sun.