4. A cellular telephone operates in the Still to QEDMHZ band and has a power output of 0.501] W from an antenna lll cm long. [a] Find the average magnitude of the Poynting vector 4.130 cm from the antenna, at the location of a typical person's head. Assume that the antenna emits energy with spherical wave fronts. {The actual radiation from antennas follows a more complicated pattern.) [b] The ANSLI'IEEE (29511991 maximum exposure standard is 115? rnl-"Il'cm2 for persons living near cellular telephone base stations, who would be continuously exposed to the radiation. Compare the answer to part {a} with this standard