PH 122 Lecture Notes - Microwave Oven, Field Strength, Photon Energy
Document Summary
The speed of electromagnetic waves is the same for all waves regardless of wavelength. A typical analog cell phone has a frequency of 850 mhz; a digital phone a frequency of 1950. Compared to the signal from an analog phone, the digital signal has shorter wavelength and higher photon energy. A radio tower emits two 50 w signals, one an am signal at a frequency of 850 khz, one an fm signal at a frequency of 85 mhz. Therefore the am signal has more photons per second. Intensity of an electromagnetic wave with field amplitudes e0 and b0. Inside the cavity of a microwave oven, the 2. 4 ghz electromagnetic waves have an intensity of 5. 0 kw/m2. A digital cell phone emits a 1. 9 ghz electromagnetic wave with total power 0. 60 w. At a cell phone tower 2. 0 km away, what is the intensity of the wave? (assume that the wave spreads out uniformly in all directions. )
