Scattered ultraviolet radiation underneath a shade-cloth.

TL;DRAbstract

Ultraviolet (UV) radiometers and polysulphone film badges were used to study scattered UV radiation from sunlight underneath a shade-cloth of a size about 70 x 100 cm2. The transmittance of erythemal UV radiation through the shade-cloth was found to be 0.14 +/- 0.03. The results of the measurements were used to derive the shade ratio, defined as the ratio of the erythema UV irradiance or dose in the shadow to that outside the shadow. It was found that the shade ratio is not the same as the transmittance. Its value depends on the height and the orientation of the irradiated object. For a horizontal detector, the shade ratio decreases by more than 20% as the detector height increased from 0.37 m to 1.36 m. At a height of 1.36 m, the shade ratio decreased by about 100% as the horizontal meter was rotated to the vertical direction. The value of the shade-ratio (0.11) approached the value of the transmittance (0.14) as the height (1.53 m) of the horizontal meter approached the height of the

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