[" 20.The intensity of electromagnetic wave at a "],[" distance of 1"Km" from a source of power "12.56],[" kw.is "],[[" 1) "10^(-3)Wm^(-2)," 2) "4times10^(-3)Wm^(-2)],[" 3) "12.56times10^(-3)Wm^(-2)," 4) "1.256times10^(-3)Wm^(-2)]]