Sentence:  Here the stripped panelling was warmly gold and the pictures, mostly of the English school, were mellow and gentle in the afternoon <WSD>light</WSD>. 
Meaning of the word marked with <WSD> tags:  Visible electromagnetic radiation. The human eye can typically detect radiation (light) in the wavelength range of about 400 to 750 nanometers. Nearby shorter and longer wavelength ranges, although not visible, are commonly called ultraviolet and infrared light.