- Lines and italic values indicate when solar radiance dropped below UV light irradiance at 5 m (dotted line), 10 m (solid line) and 20 m (bold and thick line) distance from the lights (365 nm: 0.169, 0.042 and 0.011 Watt/m2 respectively; 400 nm: 0.646, 0.162 and 0.040 Watt/m2 respectively). In grey the daytime period is indicated when the UV lights were off