To investigate thermal sensation caused by the different wavelength of solar radiation, subjective experiments were carried out with 63 subjects, namely 30 males and 33 females. Three kinds of wavelength bands including almost visible (0.3-0.8 μm), near-infrared (0.8-1.35 μm) and middle-infrared (1.7-2.3 μm) were tested at radiant intensity of 1220 W/m^2. Those were irradiated on back of subjects' hand through a hole with 4cm diameter. Experimental results showed that subjects felt hotter and more painful for the visible and middle-infrared radiation than those caused by the near-nfrared one. In addition, the ratio of stimulative sensitivity for the equivalent radiant intensity was calculated to be 1.43 : 1.00 : 1.67 for visible:near-infrared:middle-infrared.
