Question

Consider a cell phone that emits electromagnetic radiation with a frequency of 1.0 GHz and with a power of 50 W. (a) What is the electric field amplitude at a distance 1130 m away from the phone? Assume it radiates as a point source. Submit Answer Tries 0/8 (b) If your ear is only about 10 cm from the source of radiation, what is the electric field amplitude at your ear as you use the phone? Again assume the phone radiates as a point source. Submit Answer Tries 0/8 (c) If the phone can be turned on and stays transmitting for 2 h before discharging the battery, how much energy can be stored in the battery? Submit Answer Tries 0/8

Answer 1

(a) The electric field is P=-&,CE A 2 1 100 = = (8.85x10-12)(3x10°)(4x)(1130)? E 2 E = 0.0685 V/m =0.069 V/m (b) At distance is r = 0.1 m P=&CEA 2 100 = (81.85x10-1)(3x10°)(47)(0.1)? E? 2 E = 774.24 V/m (C) The energy is E = Pt = (100)(2)(3600) = 7.2x10 J