LIGHT SOURCES AND DETECTORS 



slightly higher temperature (Figures 28.5 and 28.6). The sun approximates 

 to a full radiator at a temperature of 5,400°K, where about 40 per cent of 

 the radiant energy is detected by the eye. In the case of tungsten filament 



c< 300 



E 



200 



c 



.Q 



« 



QC 



SIOOO 15P00 



Wavelength 



Figure 28.5 Comparison between the spectral distribution of the emission 

 from an ideal black body and a tungsten surface, both at 2,870°K 



TABLE 2 

 Colour Temperatures of Common Sources — from Spencer^ 



338 



