Spectral Characteristics of Light Sources for Fading and Degradation Testing

The spectral distribution of energy in the visible and ultra–violet regions has been measured for the enclosed carbon are commonly employed in fading test apparatus. Tests have boen made on both D. C. and A. C. arcs, and the effect of electrical loading, asymmetrical polar distribution, and obscuration of the enclosing globe has been investigated. Certain data are also presented for the high–intensity carbon arc and for three types of metal–vapour electric discharge lamp likely to be suitable for photochemical work. Comparison is made with incandescent tungsten sources and with sunlight for corresponding spectral regions.