228 



REFLECTION AND TRANSMISSION OF RADIO WAVES 



The theory of microwave absorption by oxygen and water vapor has been 

 developed by Van Vleck.^^ The oxygen absorption is due to a large number 

 of overlapping resonance lines, resulting in peaks centered at wavelengths 

 of 5 and 2.5 mm, while water vapor has an absorption peak at 1.35 cm. 

 Fig. 4-46 shows the theoretical attenuation due to oxygen for paths at sea 



6,000 30,000 100,000 



FREQUENCY (f) Mc 

 Fig. 4-46 Atmospheric Attenuation Due to Oxygen. 



level and at 4 km. Fig. 4-47 shows the theoretical water vapor attenuation 

 in an atmosphere containing 1 per cent water vapor. The attenuation is 

 closely proportional to the water vapor concentration. Experimental points 



35See reference of footnote 25, pp. 646-664. 



